Remote authentication of an object using a signature encoded in a number of data portions

ABSTRACT

A method of authenticating an object in which a computer system receives indicating data from a sensing device. The indicating data is generated in response to sensing of coded data and is indicative of an identity of the object and a plurality of signature fragments, the signature being a digital signature of at least part of the identity. The computer system uses the indicating data to determine the identity and the plurality of signature fragments. The plurality of signature fragments are then used to determined a determined signature, which is in turn used to generate a generated identity. The identity is then compared to the generated identity to authenticate the object.

CROSS REFERENCES TO RELATED APPLICATION

The present application is a continuation of U.S. application Ser. No. 11/041,698 filed on Jan. 25, 2005, the entire contents of which are herein incorporated by reference.

FIELD OF THE INVENTION

The present invention broadly relates to a method and apparatus for the protection of products and security documents using machine readable tags disposed on or in a surface of the product or security document.

CROSS REFERENCE TO OTHER RELATED APPLICATIONS

The following applications have been filed by the Applicant simultaneously with this application:

11863253 11863255 11/863257 11863258 11863268 11863269 11863270 11863271 11863273 11863263 11863264 11863265 11863267

The disclosures of these co-pending applications are incorporated herein by reference. The above applications have been identified by their filing docket number, which will be substituted with the corresponding application number, once assigned.

The following applications were filed by the Applicant simultaneously with the parent application, application Ser. No. 11/041,698:

11/041650 11/041651 11/041652 11/041649 11/041610 11/041609 11/041626 11/041627 11/041624 11/041625 11/041556 11/041580 11/041723 11/041648

The disclosures of these co-pending applications are incorporated herein by reference.

Various methods, systems and apparatus relating to the present invention are disclosed in the following co-pending applications and granted patents filed by the applicant or assignee of the present invention. The disclosures of all of these co-pending applications and granted patents are incorporated herein by cross-reference.

7249108 6566858 6331946 6246970 6442525 7346586 09/505951 6374354 7246098 6816968 6757832 6334190 6745331 7249109 7197642 7093139 10/636263 10/636283 10/866608 7210038 10/902883 10/940653 10/942858 10/815621 7243835 10/815630 10/815637 10/815638 7251050 10/815642 7097094 7137549 10/815618 7156292 10/815635 10/815647 10/815634 7137566 7131596 7128265 7197374 7175089 10/815617 10/815620 7178719 10/815613 7207483 7296737 7270266 10/815614 10/815636 7128270 10/815609 7150398 7159777 10/815610 7188769 7097106 7070110 7243849 6623101 6406129 6505916 6457809 6550895 6457812 6428133 7204941 7282164 10/815628 10/407212 6746105 7246886 7128400 7108355 6991322 7287836 7118197 10/728784 10/728783 7077493 6962402 10/728803 7147308 10/728779 7118198 7168790 7172270 7229155 6830318 7195342 7175261 10/773183 7108356 7118202 10/773186 7134744 10/773185 7134743 7182439 7210768 10/773187 7134745 7156484 7118201 7111926 10/773184 7156289 7178718 7225979 09/575197 7079712 6825945 7330974 6813039 7190474 6987506 6824044 7038797 6980318 6816274 7102772 7350236 6681045 6678499 6679420 6963845 6976220 6728000 7110126 7173722 6976035 6813558 6766942 6965454 6995859 7088459 6720985 7286113 6922779 6978019 6847883 7131058 7295839 09/607843 09/693690 6959298 6973450 7150404 6965882 7233924 09/575181 09/722174 7175079 7162259 6718061 10/291523 10/291471 7012710 6825956 10/291481 7222098 10/291825 7263508 7031010 6972864 6862105 7009738 6989911 6982807 10/291576 6829387 6714678 6644545 6609653 6651879 10/291555 7293240 10/291592 10/291542 7044363 7004390 6867880 7034953 6987581 7216224 10/291821 7162269 7162222 7290210 7293233 7293234 6850931 6865570 6847961 10/685523 10/685583 7162442 10/685584 7159784 10/804034 10/793933 6889896 10/831232 7174056 6996274 7162088 10/943874 10/943872 10/944044 7259884 10/944043 7167270 10/943877 6986459 10/954170 7181448 10/981626 10/981616 7324989 7231293 7174329 10/992713 7295922 7200591 11/020106 11/020260 11/020321 11/020319 11/026045 7068382 7007851 6957921 6457883 10/743671 7044381 7094910 7091344 7122685 7038066 7099019 7062651 6789194 6789191 10/900129 7278018 10/913350 10/982975 10/983029 6644642 6502614 6622999 6669385 6827116 7011128 10/949307 6549935 6987573 6727996 6591884 6439706 6760119 7295332 7064851 6826547 6290349 6428155 6785016 6831682 6741871 6927871 6980306 6965439 6840606 7036918 6977746 6970264 7068389 7093991 7190491 10/901154 10/932044 10/962412 7177054 10/962552 10/965733 10/965933 10/974742 10/982974 7180609 10/986375 6982798 6870966 6822639 6474888 6627870 6724374 6788982 7263270 6788293 6946672 6737591 7091960 09/693514 6792165 7105753 6795593 6980704 6768821 7132612 7041916 6797895 7015901 7289882 7148644 10/778056 10/778058 10/778060 10/778059 10/778063 10/778062 10/778061 10/778057 7096199 7286887 10/917467 10/917466 7324859 7218978 7245294 7277085 7187370 10/917436 10/943856 10/919379 7019319 10/943878 10/943849 7043096 7055739 7233320 6830196 6832717 7182247 7120853 7082562 6843420 10/291718 6789731 7057608 6766944 6766945 7289103 10/291559 7299969 10/409864 7108192 7111791 7077333 6983878 10/786631 7134598 10/893372 6929186 6994264 7017826 7014123 7134601 7150396 10/971146 7017823 7025276 10/492169 10/492152 10/492168 10/492161 7308148 10/502575 10/683151 10/683040 10/510391 10/510392 10/778090 6957768 09/575172 7170499 7106888 7123239 6982701 6982703 7227527 6786397 6947027 6975299 7139431 7048178 7118025 6839053 7015900 7010147 7133557 6914593 10/291546 6938826 7278566 7123245 6992662 6593166 7132679 6940088 10/727181 10/727162 10/727163 10/727245 7121639 7165824 7152942 10/727157 7181572 7096137 7302592 7278034 7188282 10/727159 10/727180 10/727179 10/727192 10/727274 10/727164 10/727161 10/727198 10/727158 10/754536 10/754938 10/727160 10/934720 10/296522 6795215 7070098 7154638 6805419 6859289 6977751 6398332 6394573 6622923 6747760 6921144 10/884881 7092112 7192106 10/854521 10/854522 10/854488 7281330 10/854503 7328956 10/854509 7188928 7093989 10/854497 10/854495 10/854498 10/854511 10/854512 10/854525 10/854526 10/854516 7252353 10/854515 7267417 10/854505 10/854493 7275805 7314261 10/854490 7281777 7290852 10/854528 10/854523 10/854527 10/854524 10/854520 10/854514 10/854519 10/854513 10/854499 10/854501 7266661 7243193 10/854518 10/854517 10/934628 6454482 6808330 6527365 6474773 6550997 7093923 6957923 7131724 10/949288 7168867 7125098 7195336

BACKGROUND

Currently there are two main types of technologies offering alternative methods of unique product item identification, such as EPCs, namely:

-   -   2D optical barcodes, and     -   RFID.

A 2D optical barcode consists of a composite image that can store about 2,000 bytes of data along two dimensions. The Uniform Code Council and European Article Numbering (EAN) International have standardized a range of 2D barcodes, all with a significantly larger data capacity than the existing EPC.

2D optical barcodes are now widely used in the global pharmaceutical industry. In the United States, the Food and Drug Administration (FDA) has mandated their use on all pharmaceutical goods manufactured within its jurisdiction to identify product lines. The main advantage driving their acceptance is that they are inexpensive to produce.

The main disadvantage of 2D optical barcodes is that they are often difficult to read due to label damage and a direct ‘line-of-sight’ is needed for scanning. In addition to this, 2-D optical barcodes are unsightly and therefore detrimental to the packaging of the product. This problem is exacerbated in the case of pharmaceuticals, which generally use small packaging, but require a relatively large bar-code which can therefore obscure a substantial part of the packaging.

In the case RFID tags, these can again provide unique product item identification encoded in the form of an EPC. However, there are also some disadvantages that make RFID tags unsuitable for some products.

First, RFID tags are costly to produce. Secondly, the presence of metals, liquids and other electromagnetic frequency (EMF) signals can interfere with RFID tag scanners, and thus seriously jeopardize the reliability and integrity of the RFID system. Thirdly tags can be read remotely without knowledge of the tag holder, thereby raising privacy concerns.

Surface Coding Background

The netpage surface coding consists of a dense planar tiling of tags. Each tag encodes its own location in the plane. Each tag also encodes, in conjunction with adjacent tags, an identifier of the region containing the tag. This region ID is unique among all regions. In the netpage system the region typically corresponds to the entire extent of the tagged surface, such as one side of a sheet of paper.

The surface coding is designed so that an acquisition field of view large enough to guarantee acquisition of an entire tag is large enough to guarantee acquisition of the ID of the region containing the tag. Acquisition of the tag itself guarantees acquisition of the tag's two-dimensional position within the region, as well as other tag-specific data. The surface coding therefore allows a sensing device to acquire a region ID and a tag position during a purely local interaction with a coded surface, e.g. during a “click” or tap on a coded surface with a pen.

The use of netpage surface coding is described in more detail in the following copending patent applications, U.S. Ser. No. 10/815,647, entitled “Obtaining Product Assistance” filed on 2 Apr. 2004; and U.S. Ser. No. 10/815,609, entitled “Laser Scanner Device for Printed Product Identification Cod” filed on 2 Apr. 2004.

Cryptography Background

Cryptography is used to protect sensitive information, both in storage and in transit, and to authenticate parties to a transaction. There are two classes of cryptography in widespread use: secret-key cryptography and public-key cryptography.

Secret-key cryptography, also referred to as symmetric cryptography, uses the same key to encrypt and decrypt a message. Two parties wishing to exchange messages must first arrange to securely exchange the secret key.

Public-key cryptography, also referred to as asymmetric cryptography, uses two encryption keys. The two keys are mathematically related in such a way that any message encrypted using one key can only be decrypted using the other key. One of these keys is then published, while the other is kept private. They are referred to as the public and private key respectively. The public key is used to encrypt any message intended for the holder of the private key. Once encrypted using the public key, a message can only be decrypted using the private key. Thus two parties can securely exchange messages without first having to exchange a secret key. To ensure that the private key is secure, it is normal for the holder of the private key to generate the public-private key pair.

Public-key cryptography can be used to create a digital signature. If the holder of the private key creates a known hash of a message and then encrypts the hash using the private key, then anyone can verify that the encrypted hash constitutes the “signature” of the holder of the private key with respect to that particular message, simply by decrypting the encrypted hash using the public key and verifying the hash against the message. If the signature is appended to the message, then the recipient of the message can verify both that the message is genuine and that it has not been altered in transit.

Secret-key can also be used to create a digital signature, but has the disadvantage that signature verification can also be performed by a party privy to the secret key.

To make public-key cryptography work, there has to be a way to distribute public keys which prevents impersonation. This is normally done using certificates and certificate authorities. A certificate authority is a trusted third party which authenticates the association between a public key and a person's or other entity's identity. The certificate authority verifies the identity by examining identity documents etc., and then creates and signs a digital certificate containing the identity details and public key. Anyone who trusts the certificate authority can use the public key in the certificate with a high degree of certainty that it is genuine. They just have to verify that the certificate has indeed been signed by the certificate authority, whose public key is well-known.

To achieve comparable security to secret-key cryptography, public-key cryptography utilizes key lengths an order of magnitude larger, i.e. a few thousand bits compared with a few hundred bits.

Schneier B. (Applied Cryptography, Second Edition, John Wiley & Sons 1996) provides a detailed discussion of cryptographic techniques.

SUMMARY OF THE INVENTION

In a first broad form of the invention provides coded data for disposal on or in a surface, the coded data including a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding.

Optionally, the padding is associated with and unique to the identity, the padding being at least one of: a predetermined number; and, a random number.

Optionally, each data portion encodes a signature fragment.

Optionally, the entire signature is encoded within a plurality of data portions.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least part of the signature.

Optionally, the coded data is substantially invisible to an unaided human.

Optionally, the coded data is printed on the surface using at least one of: an invisible ink; and, an infrared-absorptive ink.

Optionally, the coded data is provided substantially coincident with visible human-readable information.

Optionally, at least some of the coded data portions encode data indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; an identity of a signature fragment; and, units of indicated locations.

Optionally, the coded data includes at least one of: redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: an object defining the surface; the surface; a region of the surface; and, an object associated with the surface.

Optionally, at least one coded data portion further encodes at least a fragment of a data object.

Optionally, the data object includes at least one of: the digital signature; Multipurpose Internet Mail Extensions (MIME) data; text data; image data; audio data; video data; application data; contact data; business card data; and, directory data.

Optionally, the surface is associated with an object, the object including at least one of: an item of manufacture; a pharmaceutical item; a currency note; a check; a credit or debit card; a redeemable ticket, voucher, or coupon; a lottery ticket or instant win ticket; and, an identity card or document, such as a driver's license or passport.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is adapted to be sensed by a sensing device to allow determination of the identity and, at least part of the signature.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the surface having disposed therein or thereon coded data according to claim 1, the coded data encoding an identity of the object.

Optionally, the coded data including a plurality of coded data portions, each coded data portion encoding at least a fragment of a data object, the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the coded data is disposed in or on a surface of an object.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including: sensing the coded data, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including: sensing the coded data; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object using a processor and being provided on or in a surface associated with the object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object using a processor and being disposed thereon or therein a surface associated with the object, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used by a device for authenticating an object and being provided on or in a surface associated with the objected, the device including: a sensor for sensing the coded data, the coded data encoding: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; and, a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In a second broad form the invention provides coded data for disposal on or in a surface, the coded data including a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, wherein the padding is associated with and unique to the identity, the padding being at least one of: a predetermined number; a random number.

Optionally, each data portion encodes a signature fragment.

Optionally, the entire signature is encoded within a plurality of data portions.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least part of the signature.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is substantially invisible to an unaided human.

Optionally, the coded data is printed on the surface using at least one of an invisible ink; and, an infrared-absorptive ink.

Optionally, the coded data is provided substantially coincident with visible human-readable information.

Optionally, at least some of the coded data portions encode data indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; an identity of a signature fragment; and, units of indicated locations.

Optionally, the coded data includes at least one of: redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: an object defining the surface; the surface; a region of the surface; and, an object associated with the surface.

Optionally, at least one coded data portion further encodes at least a fragment of a data object.

Optionally, the data object includes at least one of: the digital signature; Multipurpose Internet Mail Extensions (MIME) data; text data; image data; audio data; video data; application data; contact data; business card data; and, directory data.

Optionally, the surface is associated with an object, the object including at least one of: an item of manufacture; a pharmaceutical item; a currency note; a check; a credit or debit card; a redeemable ticket, voucher, or coupon; a lottery ticket or instant win ticket; and, an identity card or document, such as a driver's license or passport.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is adapted to be sensed by a sensing device to allow determination of the identity; and, at least part of the signature.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, an object associated with a surface, the surface having disposed therein or thereon coded data, wherein the coded data encodes an identity of the object.

Optionally, the coded data being disposed on or in a surface, the coded data including a plurality of coded data portions, each coded data portion encoding: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the coded data being provided on or in a surface of an object.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including: sensing the coded data, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including: sensing the coded data; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object using a processor and being provided on or in a surface associated with the object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object using a processor and being provided therein or thereon a surface associated with the object, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used by a device for authenticating an object and being provided on or in a surface associated with the object, the device including: a sensor for sensing coded, the coded data encoding: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; and, a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In a third broad form the invention provides coded data for disposal on or in a surface, the coded data including a plurality of coded data portions, each coded data portion encoding: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the data object includes at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding.

Optionally, the padding is associated with and unique to the identity, the padding being at least one of: a predetermined number; a random number.

Optionally, each data portion further encodes a signature fragment.

Optionally, the data object is encoded within a plurality of data portions.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least part of the data object.

Optionally, the coded data is substantially invisible to an unaided human.

Optionally, the coded data is printed on the surface using at least one of: an invisible ink; and, an infrared-absorptive ink.

Optionally, the coded data is provided substantially coincident with visible human-readable information.

Optionally, at least some of the coded data portions encode data indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the data object; an identity of a data object fragment; and, units of indicated locations.

Optionally, the coded data includes at least one of: redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the signature is at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: an object defining the surface; the surface; a region of the surface; and, an object associated with the surface.

Optionally, the data object includes at least one of: Multipurpose Internet Mail Extensions (MIME) data; text data; image data; audio data; video data; application data; contact data; business card data; and, directory data.

Optionally, the surface is associated with an object, the object including at least one of: an item of manufacture; a pharmaceutical item; a currency note; a check; a credit or debit card; a redeemable ticket, voucher, or coupon; a lottery ticket or instant win ticket; and, an identity card or document, such as a driver's license or passport.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is adapted to be sensed by a sensing device to allow determination of the identity; and, the data object.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, an object associated with a surface, the surface having disposed therein or thereon coded data according to claim 1, the coded data encoding an identity of the object and a data object associated with the object.

Optionally, each coded data portion further encoding at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, each coded data portion further encoding at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data being disposed in or on a surface of an object, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including: sensing the coded data, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided on or in a surface associated with the object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object and being provided, on or in a surface associated with the object, the method including: sensing the coded; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object using a processor and being provided on or in a surface associated with the object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used in a method of authenticating an object using a processor and being disposed therein or thereon a surface associated with the object, each coded data portion further encoding a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data being used by a device for authenticating an object and being provided on or in a surface associated with the object, the device including: a sensor for sensing the coded data, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; and, a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In a fourth broad form of the invention provides an object having a surface, the surface having disposed thereon or therein coded data including a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, wherein the signature is a digital signature of at least part of the identity and at least part of predetermined padding.

Optionally, the padding is associated with and unique to the identity, the padding being at least one of: a predetermined number; and, a random number.

Optionally, each data portion encodes a signature fragment.

Optionally, the entire signature is encoded within a plurality of data portions.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least part of the signature.

Optionally, the coded data is substantially invisible to an unaided human.

Optionally, the coded data is printed on the surface using at least one of: an invisible ink; and, an infrared-absorptive ink.

Optionally, the coded data is provided substantially coincident with visible human-readable information.

Optionally, at least some of the coded data portions encode data indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; an identity of a signature fragment; and, units of indicated locations.

Optionally, the coded data includes at least one of: redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, at least one coded data portion further encodes at least a fragment of a data object.

Optionally, the data object includes at least one of: the digital signature; Multipurpose Internet Mail Extensions (MIME) data; text data; image data; audio data; video data; application data; contact data; business card data; and, directory data.

Optionally, the object includes at least one of: an item of manufacture; a pharmaceutical item; a currency note; a check; a credit or debit card; a redeemable ticket, voucher, or coupon; a lottery ticket or instant win ticket; and, an identity card or document, such as a driver's license or passport.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is adapted to be sensed by a sensing device to allow determination of the identity; and, at least part of the signature.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, wherein the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the data portions are arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the object being used in a method of authenticating the object, the method including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the object being used in a method of authenticating the object, the method including: sensing coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the object being used in a method of authenticating an object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the object being used in a method of authenticating the object, the method including: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the object being used in a method of authenticating the object using a processor, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, the object being used in a method of authenticating the object using a processor, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the object being used in by a device for authenticating the object, the device including: a sensor for sensing the coded data provided on or in the surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In a fifth broad form the invention provides a method of authenticating an object, the method including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing of coded data provided on or in a surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; and, determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the method includes, in the computer system: generating authentication data indicative of success or failure of the authentication; and, transferring the authentication data to a user.

Optionally, the method includes, in the computer system, transferring the authentication data to the sensing device.

Optionally, the indicating data is further indicative of an identity of the signature part, and wherein the method includes, in the computer system: determining, using the indicating data, a received signature part identity; determining, using the received identity, a determined signature; and, determining, using the determined signature and the received signature part identity, the determined signature part.

Optionally, the method includes, in the computer system, retrieving from a data store, using the received identity, stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature parts; and, the digital signature.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the method includes, in the computer system, generating the determined signature part using the stored data and the received identity.

Optionally, the method includes, in the computer system: generating, using the stored data and the received identity, a determined signature; selecting a part of the determined signature; and, comparing the selected signature part to the received signature part.

Optionally, the method includes, in the computer system: determining, using the indicating data, a received signature part identity; selecting, using the received signature part identity, part of the determined signature.

Optionally, the method includes, in the computer system, retrieving the stored data from a remote database.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the method includes, in the computer system: determining, using the received identity, the predetermined padding; and, determining, using the predetermined padding and the received identity, the determined signature part.

Optionally, the computer system forms part of the sensing device.

Optionally, the method includes, in the computer system, communicating with the sensing device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature part; an identity of a signature part; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded data disposed on or in the surface of the object includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data disposed on or in the surface of the object includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data disposed on or in the surface of the object includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the method further includes:: sensing the coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further includes, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the method further including: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, a processor is used for authenticating the object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, a processor is used for authenticating the object, the coded data includes a number of coded data portions, each coded data portion encodes: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

In a sixth broad form the invention provides a method of authenticating an object, the method including, in a sensing device: sensing coded data provided on or in a surface associated with the object; determining, from the sensed coded data, indicating data indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; and, transferring the indicating data to a computer system, the computer system being responsive to the indicating data to: determine, using the indicating data, a received identity and a received signature part; determine, using the received identity, at least a determined signature part; compare the determined signature part to the received signature part; and, authenticate the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the coded data includes a number of coded data portions, each coded data portion encoding the identity and, at least part of the signature, the method including sensing at least one data portion.

Optionally, the method includes, in the sensing device: receiving authentication data indicative of success or failure of the authentication; and, providing an indication of the success or failure of the authentication to a user.

Optionally, the entire signature is encoded within a plurality of data portions, and wherein the method includes, in the sensing device: sensing a number of coded portions; and, generating indicating data indicative of the entire signature.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least part of the signature.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, in the sensing device, sensing the coded data using an infrared detector.

Optionally, the computer system forms part of the sensing device.

Optionally, the method includes, in the sensing device, communicating with the computer system via at least one of:

-   -   a communications network; the Internet; a mobile phone network;         and, a wireless connection.

Optionally, method includes, in the sensing device, generating indicating indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

In a seventh broad form the invention provides a method of authenticating an object, the method including: sensing coded data provided on or in a surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; and, determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the method includes, generating an indication of success or failure of the authentication.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encoding: an identity; and, at least a signature fragment; wherein the method includes sensing at least one coded data portion.

Optionally, the coded data is further indicative of an identity of the signature part, and wherein the method includes: determining a signature part identity of the sensed signature part; determining, using the sensed identity, a determined signature; and, selecting, using signature part identity of the sensed signature part, and from the determined signature, the determined signature part.

Optionally, the method includes, retrieving from a data store, using the sensed identity, stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature parts; and, the digital signature.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the method includes, determining the determined signature part using the stored data and the sensed identity.

Optionally, the method includes, retrieving the stored data from a remote database.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least one signature part.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, sensing the coded data using an infrared detector.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the method includes: determining, using the identity, the predetermined padding; and, generating, using the predetermined padding and the determined signature, the generated identity.

Optionally, the method is performed in a sensing device having: an image sensor for sensing the coded data; and, a processor for authenticating the object.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature part; an identity of a signature part; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded data includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data including a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the coded data includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the method further including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, a processor is used in a method of authenticating the object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the object being associated with the surface having disposed thereon or therein the coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the method is used by a device for authenticating the object, the device including: a sensor for sensing the coded data provided on or in the surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In an eighth broad form the invention provides a method of authenticating an object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing of coded data provided on or in a surface associated with the object, the indicating data being indicative of: an identity of the object; a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the method includes, in the computer system: generating authentication data indicative of success or failure of the authentication; and, transferring the authentication data to a user.

Optionally, the method includes, in the computer system, transferring the authentication data to the sensing device.

Optionally, the indicating data is further indicative of the identity of each of the plurality of signature fragments, and wherein the method includes, in the computer system: determining, from the indicating data, the signature fragment identity of each of the plurality of signature fragments; and, determining, using the determined signature fragment identities, the determined signature.

Optionally, the method includes, in the computer system: retrieving from a data store, using the received identity, stored data including at least one of: padding associated with the signature; a private key; and, a public key; and, generating, using the stored data and the determined signature, the generated identity.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the method includes, in the computer system, retrieving the stored data from a remote database.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the method includes, in the computer system: determining, using the received identity, the predetermined padding; and, generating, using the predetermined padding and the determined signature, the generated identity.

Optionally, the plurality of signature fragments are indicative of the entire signature.

Optionally, the computer system forms part of the sensing device.

Optionally, the method includes, in the computer system, communicating with the sensing device via at least one of:

-   -   a communications network; the Internet; a mobile phone network;         and, a wireless connection.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature fragment; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the coded data includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the method further includes, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the method further including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the method is used by a device for authenticating the object, the device including: a sensor for sensing coded data provided on or the a surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In a ninth broad form the invention provides a method of authenticating an object, the method including, in a sensing device: sensing coded data provided on a surface associated with the object; determining, from the sensed coded data, indicating data indicative of: an identity of the object; a plurality of signature fragments, the signature being a digital signature of at least part of the identity; transferring the indicating data to a computer system, the computer system being responsive to the indicating data to: determine, using the indicating data, the identity and the plurality of signature fragments; determine, using the plurality of signature fragments, a determined signature; generate, using the determined signature and a key, a generated identity; compare the identity to the generated identity; and, authenticate the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the method includes, in the sensing device: receiving authentication data indicative of success or failure of the authentication; and, providing an indication of the success or failure of the authentication to a user.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encoding: an identity; and, at least a signature fragment; wherein the method includes, in the sensing device, sensing a plurality of coded data portions to thereby determine indicating data.

Optionally, each coded data portion encodes a signature fragment identity, and wherein the method includes, in the sensing device: determining the signature fragment identity of each determined signature fragment; and, generating the indicating data, using the determined signature fragment identities, the determined signature.

Optionally, the plurality of signature fragments are indicative of the entire signature.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least one signature fragment.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, in the sensing device, sensing the coded data using an infrared detector.

Optionally, the computer system forms part of the sensing device.

Optionally, the method includes, in the sensing device, communicating with the computer system via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the method includes, in the sensing device, generating indicating indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature fragment; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

In a tenth broad form the invention provides a method of authenticating an object, the method including: sensing coded data provided on or in a surface associated with the object; determining, from the sensed coded data: an identity of the object; a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally the method includes, generating an indication of success or failure of the authentication.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encoding: an identity; and, at least a signature fragment; wherein the method includes sensing a plurality of coded data portions to thereby determine the plurality of signature fragments.

Optionally, each coded data portion encodes a signature fragment identity, and wherein the method includes: determining the signature fragment identity of each determined signature fragment; and, determining, using the determined signature fragment identities, the determined signature.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least one signature fragment.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, sensing the coded data using an infrared detector.

Optionally, the plurality of signature fragments are indicative of the entire signature.

Optionally, the method includes: retrieving from a data store, using the identity, stored data indicative of at least one of: padding associated with the signature; a private key; and, a public key; and, generating, using the stored data and the determined signature, the generated identity.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the method includes, retrieving the stored data from a remote database.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the method includes: determining, using the identity, the predetermined padding; and, generating, using the predetermined padding and the determined signature, the generated identity.

Optionally, the method includes, in a sensing device: using a sensor, sensing the coded data; using a processor: determining, from the sensed coded data: the identity of the object; the plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, the determined signature; generating, using the determined signature and the key, the generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature fragment; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the coded data includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the method further includes, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the method further including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the method is used by a device for authenticating the object, the device including: a sensor for sensing coded data provided on or the a surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the sensed identity and the at least one sensed signature part.

In an eleventh broad form the invention provides a method of authenticating an object using a processor, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of coded data provided on or in a surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the method includes, in the processor: generating authentication data indicative of success or failure of the authentication; and, transferring the authentication data to a user.

Optionally, the method includes, in the processor, transferring the authentication data to a sensing device.

Optionally, the indicating data is further indicative of an identity of the signature part, and wherein the method includes, in the processor: determining, using the indicating data, a received signature part identity; selecting, using the received identity, a part of the determined signature; and, authenticating the object by comparing the determined signature part and the at least one received signature part.

Optionally, the method includes, in the processor, retrieving from a data store, using the received identity, stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature parts; and, the digital signature.

Optionally, the method includes, in the processor, generating the determined signature part using the stored data and the received identity.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, sensing the coded data using an infrared detector.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the method includes, in the processor: determining, using the received identity, the predetermined padding; and, determining, using the predetermined padding and the received identity, the determined signature part.

Optionally, the processor forms part of a sensing device, and wherein the method includes, receiving the indicating data from a sensor in the sensing device.

Optionally, the processor communicates with a sensing device which generates the indicating data, and wherein the method includes, receiving the indicating data from the sensing device.

Optionally, the method includes, in the processor, communicating with the sensing device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature part; an identity of a signature part; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the processor determines the determined signature by communicating with a second processor which generates the determined signature using the received identity and the secret key.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least one signature part.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the method includes, in the processor, retrieving the stored data from a remote database.

Optionally, the coded includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the method further includes, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, wherein the method further includes: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally, the method is used by a device for authenticating the object, the device including: a sensor for sensing coded data provided on or the a surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; and, authenticating the object using the sensed identity and the at least one sensed signature part.

In a twelfth broad form the invention provides a method of authenticating an object using a processor, the method including, in a sensing device: sensing coded data provided on or in a surface associated with the object; determining, from the sensed coded data, indicating data indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; providing the indicating data to the processor, the processor being responsive to the indicating data to: generate, using the identity and a secret key, the signature; compare the determined signature to the at least part of the signature; and, authenticate the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

In a thirteenth broad form the invention provides a processor for authenticating an object, the object being associated with a surface having disposed thereon or therein coded data indicative of: an identity of the object; and, at least part of a signature, the signature being indicative of a digital signature of at least part of the identity. wherein the processor: receives indicating data, the indicating data being generated in response to sensing of the coded data, the indicating data being indicative of the identity and at least part of the signature; determines, using the indicating data, the identity and the at least part of the signature; generates, using the determined identity and a secret key, a determined signature; compares the determined signature to the at least part of the signature; and, authenticates the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data includes a number of coded data portions, each coded data portion encoding the identity and, at least part of the signature, the method including sensing at least one data portion.

Optionally, the method includes, in the sensing device: receiving authentication data indicative of success or failure of the authentication; and, providing an indication of the success or failure of the authentication to a user.

Optionally, the entire signature is encoded within a plurality of data portions, and wherein the method includes, in the sensing device: sensing a number of coded portions; and, generating indicating data indicative of the entire signature.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least part of the signature.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, in the sensing device, sensing the coded data using an infrared detector.

Optionally, the processor forms part of the sensing device.

Optionally, the method includes, in the sensing device, communicating with the processor via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, method includes, in the sensing device, generating indicating indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the processor determines the determined signature by communicating with a second processor which generates the determined signature using the received identity and the secret key.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the processor: generates authentication data indicative of success or failure of the authentication; and, transfers the authentication data to a user.

Optionally, the processor transfers the authentication data to a sensing device.

Optionally, the indicating data is further indicative of an identity of the signature part, and wherein the processor: determines, using the indicating data, a received signature part identity; selects, using the received identity, a part of the determined signature; and, authenticates the object by comparing the determined signature part and the at least one received signature part.

Optionally, the processor retrieves from a data store, using the received identity, stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature parts; and, the digital signature.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the processor, generates the determined signature part using the stored data and the received identity.

Optionally, the processor retrieves the stored data from a remote database.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the processor: determines, using the received identity, the predetermined padding; and, determines, using the predetermined padding and the received identity, the determined signature part.

Optionally, the processor forms part of a sensing device.

Optionally, the processor communicates with a sensing device which generates the indicating data, and wherein the processor receives the indicating data from the sensing device.

Optionally, processor communicates with the sensing device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature part; an identity of a signature part; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the processor determines the determined signature by communicating with a second processor which generates the determined signature using the received identity and the secret key.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

In a fourteenth broad form the invention provides a method of authenticating an object using a processor, the object being associated with a surface having disposed thereon or therein coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity. the method including, in the processor: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the method includes, in the processor: generating authentication data indicative of success or failure of the authentication; and, transferring the authentication data to a user.

Optionally, the method includes, in the processor, transferring the authentication data to a sensing device.

Optionally, the indicating data is further indicative of an identity of each signature fragment, and wherein the method includes, in the processor: determining, using the indicating data, a received signature fragment identity for each received signature fragment; and, determining, using the received signature fragment identity for each received signature fragment, a determined signature; and, determining, using the determined signature and the secret key, the determined identity.

Optionally, the method includes, in the processor, retrieving from a data store, using the received identity, stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature fragments; and, the digital signature.

Optionally, the method includes, in the processor, determining the determined identity using the stored data and the received signature fragments.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, sensing the coded data using an infrared detector.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the method includes, in the processor: determining, using the received identity, the predetermined padding; and, determining, using the predetermined padding and the received signature fragments, the determined identity.

Optionally, the processor forms part of a sensing device, and wherein the method includes, receiving the indicating data from a sensor in the sensing device.

Optionally, the processor communicates with a sensing device which generates the indicating data, and wherein the method includes, receiving the indicating data from the sensing device.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface, a size of the data portions; a size of the signature; a size of the signature fragment; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the indicating data is indicative of the entire signature.

Optionally, the processor determines the determined identity by communicating with a second processor which generates the determined identity using the received signature fragments and the secret key.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least one signature fragment.

Optionally, the method includes, in the processor, retrieving the stored data from a remote database.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the method includes, in the processor, communicating with the sensing device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the coded includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the method further includes, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the method further includes: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, a processor is used to authenticate the object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, the method is used by a device for authenticating the object, the device including: a sensor for sensing coded data provided on or the a surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; and, authenticating the object using the sensed identity and the at least one sensed signature part.

In a fifteenth broad form the invention provides a processor for authenticating an object, the object being associated with a surface having disposed thereon or therein coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being indicative of a digital signature of at least part of the identity. wherein the processor: receives indicating data from a sensing device, the sensing device generating the indicating data in response to sensing a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determines, from the indicating data, a received identity and a plurality of received signature fragments; determines, using the plurality of signature fragments and a secret key, a determined identity; compares the determined identity to the received identity; and, authenticates the object using the results of the comparison.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the processor: generates authentication data indicative of success or failure of the authentication; and, transfers the authentication data to a user.

Optionally, the processor transfers the authentication data to a sensing device.

Optionally, the indicating data is further indicative of an identity of each signature fragment, and wherein the processor: determines, using the indicating data, a received signature fragment identity for each received signature fragment; and, determines, using the received signature fragment identity for each received signature fragment, a determined signature; and, determines, using the determined signature and the secret key, the determined identity.

Optionally, the processor retrieves from a data store, using the received identity, stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature fragments; and, the digital signature.

Optionally, the stored data is indexed by at least one of: the identity; and, a range of identities.

Optionally, the processor determines the determined identity using the stored data and the received signature fragments.

Optionally, the processor retrieves the stored data from a remote database.

Optionally, the signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the processor: determines, using the received identity, the predetermined padding; and, determines, using the predetermined padding and the received signature fragments, the determined identity.

Optionally, the processor forms part of a sensing device.

Optionally, the processor communicates with a sensing device which generates the indicating data, and wherein the processor receives the indicating data from the sensing device.

Optionally, processor communicates with the sensing device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature fragment; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the processor determines the determined identity by communicating with a second processor which generates the determined identity using the received signature fragments and the secret key.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

In a sixteenth broad for the invention provides a method of authenticating an object using a processor, the object being associated with a surface having disposed thereon or therein coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity. the method including, in a sensing device: sensing a plurality of coded data portions; determining, from the sensed coded data portions, indicating data indicative of: the identity of the object; and, a plurality of signature fragments; providing the indicating data to the processor, the processor being responsive to the indicating data to: determine, from the indicating data, a received identity and a plurality of received signature fragments; determine, using the plurality of signature fragments and a secret key, a determined identity; compare the determined identity to the received identity; and, authenticate the object using the results of the comparison.

Optionally, the method includes, in the sensing device: receiving authentication data indicative of success or failure of the authentication; and, providing an indication of the success or failure of the authentication to a user.

Optionally, the entire signature is encoded within a plurality of data portions, and wherein the method includes, in the sensing device: sensing a number of coded portions; and, generating indicating data indicative of the entire signature.

Optionally, the coded data includes a plurality of layouts, each layout defining the position of a plurality of first symbols encoding the identity, and a plurality of second symbols defining at least one signature fragment.

Optionally, the coded data includes a plurality of tags, each coded data portion being formed from at least one tag.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the method includes, in the sensing device, sensing the coded data using an infrared detector.

Optionally, the processor forms part of the sensing device.

Optionally, the method includes, in the sensing device, communicating with the processor via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, method includes, in the sensing device, generating indicating indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes an identity of at least one of: the object; the surface; and, a region of the surface.

Optionally, the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and, a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the processor determines the determined signature by communicating with a second processor which generates the determined signature using the received identity and the secret key.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

In a seventeenth broad form the invention provides a device for authenticating an object, the device including: a sensor for sensing coded data provided on or in a surface associated with the object, the coded data encoding: an identity; and, at least one part of a signature, the signature being a digital signature of at least part of the identity; a processor for: determining, from the sensed coded data, a sensed identity and at least one sensed signature part; authenticating the object using the determined identity and the at least one sensed signature part.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the device includes, an indicator for indicating success or failure of the authentication.

Optionally, the processor is for: determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the processor is for: determining, using the sensed identity and a key, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the processor is for: determining, from the sensed coded data, a plurality of sensed signature parts; determining, using the sensed signature parts, a determined signature determining, using the determined signature and a key, a determined identity; comparing the sensed identity to the determined identity; and, authenticating the object using the results of the comparison.

Optionally, the device includes a data store, and wherein the processor: using the sensed identity, retrieves stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature parts; and, the digital signature; authenticates the object using the stored data.

Optionally, the data store is a remote database.

Optionally, the processor is for determining, from the sensed coded data, a plurality of signature parts representing the entire signature.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the sensor is at least one of: an infrared detector; and, a laser scanner.

Optionally, the device is at least one of: a document scanner; a cash register; a netpage pen; a currency scanner; a hand-held scanner; a Mobile Phone with Inbuilt scanner; an automatic telling machine; and, a vending machine.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes at least one of: an identity of at least one of: the object; the surface; and, a region of the surface; and, an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the device includes, an indicator for indicating success or failure of the authentication.

Optionally, the coded data is printed on the surface using at least one of an invisible ink and an infrared-absorptive ink, and wherein the sensor is at least one of: an infrared detector; and, a laser scanner.

Optionally, the device is at least one of: a document scanner; a cash register; a netpage pen; a currency scanner; a hand-held scanner; a Mobile Phone with Inbuilt scanner; an automatic telling machine; and, a vending machine.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes at least one of: an identity of at least one of: the object; the surface; and, a region of the surface; and, an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the processor is for determining, from the sensed coded data, indicating data indicative of a plurality of signature parts representing the entire signature.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

Optionally, the coded includes a number of coded data portions, each coded data portion encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity.

Optionally, the coded data includes a number of coded data portions, each coded data portion encodes: an identity; and, at least part of a signature, the signature being a digital signature of at least: part of the identity; and part of predetermined padding.

Optionally, the coded data includes a plurality of coded data portions, each coded data portion encodes: an identity; and, at least a fragment of a data object; the data portions being arranged such that the entire data object is encoded at least once by the plurality of coded data portions.

Optionally, the device is used in a method of authenticating an object, the method including, in a computer system: receiving indicating data from a sensing device, the sensing device generating the indicating data in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the indicating data, a received identity and a received signature part; determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the device is used in a method of authenticating an object, the method including: sensing the coded data provided on or in the surface associated with the object, the coded data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least part of the identity; determining, using the sensed coded data, a sensed identity and a sensed signature part; determining, using the sensed identity, at least a determined signature part; comparing the determined signature part to the sensed signature part; and, authenticating the object using the results of the comparison.

Optionally, the device is used in a method of authenticating an object, the method including, in a computer system: receiving from a sensing device, indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the indicating data, the identity and the plurality of signature fragments; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the device is used in a method of authenticating an object, the method including: sensing the coded data provided on or in the surface associated with the object; determining, from the sensed coded data: an identity of the object; and, a plurality of signature fragments, the signature being a digital signature of at least part of the identity; determining, using the plurality of signature fragments, a determined signature; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and, authenticating the object using the results of the comparison.

Optionally, the device is used in a method of authenticating an object, the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing the coded data provided on or in the surface associated with the object, the indicating data being indicative of: an identity of the object; and, at least part of a signature, the signature being a digital signature of at least a part of the identity; determining from the indicating data, a received identity and at least one received signature part; determining, using the received identity and a secret key, a determined signature; comparing the determined signature to the at least one received signature part; and, authenticating the object using the results of the comparison.

Optionally, the device is used in a method of authenticating an object, the coded data having a number of coded data portions, each coded data portion encoding: an identity of the object; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; the method including, in the processor: receiving indicating data, the indicating data being generated in response to sensing of a plurality of coded data portions, the indicating data being indicative of: the identity of the object; and, a plurality of signature fragments; determining, from the indicating data, a received identity and a plurality of received signature fragments; determining, using the plurality of signature fragments and a secret key, a determined identity; comparing the determined identity to the received identity; and, authenticating the object using the results of the comparison.

In an eighteenth broad form of the invention provides a device for authenticating an object, the device including: a sensor for sensing coded data provided on or in a surface associated with the object, the coded data encoding: an identity; and, at least part of a signature, the signature being a digital signature of at least part of the identity; a processor for determining, from the sensed coded data, indicating data indicative of: the identity; at least one signature part; a communications system for transferring the indicating data to a computer system, the computer system being responsive to the indicating data to authenticate the object.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the device communicates with the computer system via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the computer system is for: determining, using the received identity, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

In a nineteenth broad form the invention provides a computer system for authenticating an object, the computer system being for: receiving from a device, indicating data, the indicating data being determined in response to sensing of coded data provided on or in a surface associated with the object, the indicating data being indicative of: an identity of the object; at least part of a signature, the signature being a digital signature of at least part of the identity; determining, from the indicating data, a received identity and at least one received signature part; authenticating the object using the received identity and the at least one received signature part.

Optionally the coded data includes a number of coded data portions, and wherein each coded data portion is at least partially indicative of at least one of: at least part of the identity; at least part of the signature; and, a position of the coded data portion on the surface.

Optionally each coded data portion encodes the entire signature.

Optionally the entire signature is formed from a plurality of signature parts, and wherein each coded data portion encodes a respective signature part.

Optionally, the computer system is for: determining, using the received identity and a key, at least a determined signature part; comparing the determined signature part to the received signature part; and, authenticating the object using the results of the comparison.

Optionally, the computer system is for: determining, from the indicating data, a plurality of received signature parts; determining, using the received signature parts, a determined signature determining, using the determined signature and a key, a determined identity; comparing the received identity to the determined identity; and, authenticating the object using the results of the comparison.

Optionally, the computer system: generates authentication data indicative of success or failure of the authentication; and, transfers the authentication data to a user.

Optionally, the computer system includes a data store, and wherein the computer system: uses the sensed identity, retrieves stored data indicative of the digital signature, the stored data including at least one of: padding associated with the signature; a private key; a public key; one or more digital signature parts; and, the digital signature; authenticates the object using the stored data.

Optionally, the data store is a remote database.

Optionally, the computer system is for determining, from the sensed coded data, a plurality of signature parts representing the entire signature.

Optionally, the computer system transfers the authentication data to the device.

Optionally, the computer system communicates with the device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.

Optionally, the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; cipher-text produced using a private key, and verifiable using a corresponding public key; and cipher-text produced using RSA encryption.

Optionally, the identity includes at least one of: an identity of at least one of: the object; the surface; and, a region of the surface; and, an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.

Optionally, the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout.

In a twentieth broad form the present invention provides a method of verifying an object, wherein the method includes, in a computer system: receiving a verification request, the request being at least partially indicative of: an identity of the object; at least one signature fragment, the signature being a digital signature of at least part of the identity; determining, using the verification request, a determined identity; determining, using the determined identity, and from a database, at least one criterion relating to verification; and, comparing the received verification request to the at least one criterion; and causing the object to be verified if the at least one criterion is satisfied.

Optionally the at least one criterion relates to a limit on at least one of: a number of received verification requests; a rate of received verification requests; and, timing of received verification requests.

Optionally the limit is defined in respect of at least one of: the identity of the object; the signature; the signature fragment; a verification request source; and, the object.

Optionally the limit is proportional to a size of the signature fragment.

Optionally the method includes, in the computer system: determining, using the verification request: a request history indicative of a number of previously received verification requests; and, a corresponding limit; determining, using the verification request and the request history, a request number; and, causing the object to be verified if the request number does not exceed the corresponding limit.

Optionally the method includes, in the computer system, and in response to a verification request, updating the request history.

Optionally the request history is indicative of the timing of the received verification request.

Optionally the request history is associated with: the identity of the object; the signature; the signature fragment; a verification request source; and, the object.

Optionally the method includes, in the computer system, verifying the object by authenticating the object using the identity of the object and the at least one signature fragment.

Optionally the verification request is at least partially indicative of an identity of the signature fragment.

Optionally the object is associated with a surface having disposed thereon or therein coded data including a number of coded data portions, each coded data portion being indicative of at least the identity and a signature fragment, and wherein, in response to sensing of at least one coded data portion, a sensing device generates the verification request.

Optionally the verification request is at least partially indicative of an identity of the signature fragment, the fragment identity being based on at least one of: a number encoded within the at least one sensed coded data portion; and, a position of the at least one sensed coded data portion on the surface.

Optionally the method includes, in the computer system, only comparing the received verification request to the at least one criterion after a failed verification.

Optionally the method includes, in a computer system: receiving a verification request, the request being at least partially indicative of: an identity of the object; a concatenation of: a signature fragment, the signature fragment being a digital signature of at least part of the identity; and a random signature; determining, using the verification request, a determined identity; determining, using the concatenation, the signature fragment; and, verifying the object using the determined identity and the signature fragment.

Optionally the method includes, in the computer system: determining, using the determined identity, a key; generating, using the determined identity and the key, a generated signature; comparing the generated signature to the concatenation to thereby identify and authenticate the signature fragment.

In another broad form the present invention provides coded data for disposal on or in a surface, the coded data including a number of coded data portions, each coded data portion encoding: an identity; and, a fragment of a signature, the signature being a digital signature of at least part of the identity; and a random signature.

In another broad form the present invention provides coded data for disposal on or in a surface, the coded data including a number of coded data portions, each coded data portion being at least partially indicative of: an identity; at least fragment of a signature, the signature being a digital signature of at least part of the identity; and, a position of the coded data on the surface.

Optionally each coded data portion is at least partially indicative of a data portion identity, the data portion identity being unique for each coded data portion, the data portion identity being indicative of the position.

Optionally the coded data is disposed on or in the surface using a layout, the layout being indicative of, for each data portion identity, the position of the corresponding coded data portion.

Optionally the signature is generated using RSA encryption.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the present invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is an example of a document including Hyperlabel encoding;

FIG. 2 is an example of a system for interacting with the Hyperlabel document of FIG. 1;

FIG. 3 is a further example of system for interacting with the Hyperlabel document of FIG. 1;

FIG. 4. is a first example of a tag structure;

FIG. 5. is an example of a symbol unit cell for the tag structure of FIG. 4;

FIG. 6. is an example of an array of the symbol unit cells of FIG. 5;

FIG. 7. is an example of symbol bit ordering in the unit cells of FIG. 5;

FIG. 8. is an example of the tag structure of FIG. 4 with every bit set;

FIG. 9. is an example of tag types within a tag group for the tag structure of FIG. 4;

FIG. 10. is an example of continuous tiling of the tag groups of FIG. 9;

FIG. 11 is an example of interleaved codewords for the tag structure of FIG. 4;

FIG. 12 is an example of a code word for the tag structure of FIG. 4;

FIG. 13. is an example of a tag and its eight immediate neighbours, each labelled with its corresponding bit index in the active area map;

FIG. 14. is an alternative example of tag types within a tag group for the tag structure of FIG. 4;

FIG. 15. is an example of continuous tiling of the tag groups of FIG. 14;

FIG. 16. is an example of the orientation-indicating cyclic position codeword R for the tag group of FIG. 14;

FIG. 17. is an example of a local codeword A for the tag group of FIG. 14;

FIG. 18. is an example of distributed codewords B, C, D and E, for the tag group of FIG. 14;

FIG. 19. is an example of a layout of complete tag group;

FIG. 20. is an example of a code word for the tag group of FIG. 14;

FIG. 21. is a second example of a tag structure;

FIG. 22. is an example of a symbol unit cell for the tag structure of FIG. 21;

FIG. 23. is an example of an array of the symbol unit cells of FIG. 22;

FIG. 24. is an example of symbol bit ordering in the unit cells of FIG. 22;

FIG. 25. is an example of the tag structure of FIG. 21 with every bit set;

FIG. 26. is an example of tag types within a tag group for the tag structure of FIG. 21;

FIG. 27. is an example of continuous tiling of the tag groups of FIG. 26;

FIG. 28 is an example of an orientation indicating cyclic position codeword for the tag structure of FIG. 21;

FIG. 29 is an example of a codeword for the tag structure of FIG. 21;

FIG. 30 is an example of fragments of distributed codewords for the tag structure of FIG. 21;

FIG. 31. is an example of continuous tiling of the tag groups of FIG. 21;

FIG. 32. is an example of a tag segment of the tag groups of FIG. 21;

FIG. 33. is an example of inter-segment spacing for the tag groups of FIG. 21;

FIG. 34. is an example of the effect of inter-segment spacing on target position for the tag groups of FIG. 21;

FIG. 35. is an example of a code word for the tag group of FIG. 21;

FIG. 36. is an example of tag coordinates for the tag group of FIG. 21;

FIG. 37. is an example of tag and six immediate neighbour tags each labelled with its corresponding bit index in the active area map;

FIG. 38. is an example of a contiguous set of tags making up a data block;

FIG. 39. is an example of an expanded tag structure;

FIG. 40 is an example of a codeword for the tag structure of FIG. 39;

FIG. 41 is an example of fragments of distributed codewords for the tag structure of FIG. 39;

FIG. 42 is a second example of fragments of distributed codewords for the tag structure of FIG. 39;

FIG. 43 is an example of an item signature object model;

FIG. 44. is an example of Scanning at Retailer interactions;

FIG. 45. is an example of Online Scanning interaction detail;

FIG. 46. is an example of Offline Scanning interaction details;

FIG. 47. is an example of netpage Pen Scanning interactions;

FIG. 48. is an example of netpage Pen Scanning interaction details;

FIG. 49. is an example of a Hyperlabel tag class diagram;

FIG. 50. is an example of an item ID class diagram;

FIG. 51. is an example of a note ID class diagram

FIG. 52. is an example of a pharmaceutical ID class diagram;

FIG. 53. is an example of an Object Description, ownership and aggregation class diagram;

FIG. 54. is an example of an Object Scanning History class diagram;

FIG. 55. is an example of scanner class disgram;

FIG. 56. is an example of an object ID hot list diagram;

FIG. 57. is an example of a valid ID range class diagram;

FIG. 58. is an example of Public Key List class diagram;

FIG. 59. is an example of a Trusted Authenticator class diagram;

FIG. 60. is an example of Tagging and Tracking Object Management.

DETAILED DESCRIPTION OF THE DRAWINGS

The netpage surface coding consists of a dense planar tiling of tags. Each tag encodes its own location in the plane. Each tag also encodes, in conjunction with adjacent tags, an identifier of the region containing the tag. In the netpage system, the region typically corresponds to the entire extent of the tagged surface, such as one side of a sheet of paper.

Hyperlabel is the adaptation of the netpage tags for use in unique item identification for a wide variety of applications, including security document protection, object tracking, pharmaceutical security, supermarket automation, interactive product labels, web-browsing from printed surfaces, paper based email, and many others.

Using Memjet™ digital printing technology (which is the subject of a number of pending U.S. patent applications including U.S. Ser. No. 10/407,212), Hyperlabel tags are printed over substantially an entire surface, such as a security document, bank note, or pharmaceutical packaging, using infrared (IR) ink. By printing the tags in infrared-absorptive ink on any substrate which is infrared-reflective, the near-infrared wavelengths, and hence the tags are invisible to the human eye but are easily sensed by a solid-state image sensor with an appropriate filter. This allows machine readable information to be encoded over a large portion of the note or other surface, with no visible effect on the original note text or graphics thereon. A scanning laser or image sensor can read the tags on any part of the surface to performs associated actions, such as validating each individual note or item.

An example of such a Hyperlabel encoded document, is shown in FIG. 1. In this example, the Hyperlabel document consists of graphic data 2 printed using visible ink, and coded data 3 formed from Hyperlabel tags 4. The document includes an interactive element 6 defined by a zone 7 which corresponds to the spatial extent of a corresponding graphic 8. In use, the tags encode tag data including an ID. By sensing at least one tag, and determining and interpreting the encoded ID using an appropriate system, this allows the associated actions to be performed.

In one example, a tag map is used to define a layout of the tags on the Hyperlabel document based on the ID encoded within the tag data. The ID can also be used to reference a document description which describes the individual elements of the Hyperlabel document, and in particular describes the type and spatial extent (zone) of interactive elements, such as a button or text field. Thus, in this example, the element 6 has a zone 7 which corresponds to the spatial extent of a corresponding graphic 8. This allows a computer system to interpret interactions with the Hyperlabel document.

In position indicating techniques, the ID encoded within the tag data of each tag allows the exact position of the tag on the Hyperlabel document to be determined from the tag map. The position can then be used to determine whether the sensed tag is positioned in a zone of an interactive element from the document description.

In object indicating techniques, the ID encoded within the tag data allows the presence of the tag in a region of the document to be determined from the tag map (the relative position of the tag within the region may also be indicated). In this case, the document description can be used to determine whether the region corresponds to the zone of an interactive element.

An example of this process will now be described with reference to FIGS. 2 and 3 which show how a sensing device in the form of a netpage or Netpage pen 101, which interacts with the coded data on a printed Hyperlabel document 1, such as a security document, label, product packaging or the like.

The Netpage pen 101 senses a tag using an area image sensor and detects tag data. The Netpage pen 101 uses the sensed data tag to generate interaction data which is transmitted via a short-range radio link 9 to a relay 44, which may form part of a computer 75 or a printer 601. The relay sends the interaction data, via a network 19, to a document server 10, which uses the ID to access the document description, and interpret the interaction. In appropriate circumstances, the document server sends a corresponding message to an application server 13, which can then perform a corresponding action.

In an alternative embodiment, the PC, Web terminal, netpage printer or relay device may communicate directly with local or remote application software, including a local or remote Web server. Relatedly, output is not limited to being printed by the netpage printer. It can also be displayed on the PC or Web terminal, and further interaction can be screen-based rather than paper-based, or a mixture of the two.

Typically Netpage pen users register with a registration server 11, which associates the user with an identifier stored in the respective Netpage pen. By providing the sensing device identifier as part of the interaction data, this allows users to be identified, allowing transactions or the like to be performed.

Hyperlabel documents are generated by having an ID server generate an ID which is transferred to the document server 10. The document server 10 determines a document description and then records an association between the document description and the ID, to allow subsequent retrieval of the document description using the ID.

The ID is then used to generate the tag data, as will be described in more detail below, before the document is printed by the Hyperlabel printer 601, using the page description and the tag map.

Each tag is represented by a pattern which contains two kinds of elements. The first kind of element is a target. Targets allow a tag to be located in an image of a coded surface, and allow the perspective distortion of the tag to be inferred. The second kind of element is a macrodot. Each macrodot encodes the value of a bit by its presence or absence.

The pattern is represented on the coded surface in such a way as to allow it to be acquired by an optical imaging system, and in particular by an optical system with a narrowband response in the near-infrared. The pattern is typically printed onto the surface using a narrowband near-infrared ink.

In the Hyperlabel system the region typically corresponds to the surface of an entire product item, or to a security document, and the region ID corresponds to the unique item ID. For clarity in the following discussion we refer to items and item IDs (or simply IDs), with the understanding that the item ID corresponds to the region ID.

The surface coding is designed so that an acquisition field of view large enough to guarantee acquisition of an entire tag is large enough to guarantee acquisition of the ID of the region containing the tag. Acquisition of the tag itself guarantees acquisition of the tag's two-dimensional position within the region, as well as other tag-specific data. The surface coding therefore allows a sensing device to acquire a region ID and a tag position during a purely local interaction with a coded surface, e.g. during a “click” or tap on a coded surface with a pen.

A wide range of different tag structures can be used, and some examples will now be described.

First Example Tag Structure

FIG. 4 shows the structure of a complete tag. Each of the four black circles is a target. The tag, and the overall pattern, has four-fold rotational symmetry at the physical level.

Each square region represents a symbol, and each symbol represents four bits of information.

FIG. 5 shows the structure of a symbol. It contains four macrodots, each of which represents the value of one bit by its presence (one) or absence (zero).

The macrodot spacing is specified by the parameter s throughout this document. It has a nominal value of 143 μm, based on 9 dots printed at a pitch of 1600 dots per inch. However, it is allowed to vary by ±10% according to the capabilities of the device used to produce the pattern.

FIG. 6 shows an array of nine adjacent symbols. The macrodot spacing is uniform both within and between symbols.

FIG. 7 shows the ordering of the bits within a symbol. Bit zero is the least significant within a symbol; bit three is the most significant. Note that this ordering is relative to the orientation of the symbol. The orientation of a particular symbol within the tag is indicated by the orientation of the label of the symbol in the tag diagrams. In general, the orientation of all symbols within a particular segment of the tag have the same orientation, consistent with the bottom of the symbol being closest to the centre of the tag.

Only the macrodots are part of the representation of a symbol in the pattern. The square outline of a symbol is used in this document to more clearly elucidate the structure of a tag. FIG. 8, by way of illustration, shows the actual pattern of a tag with every bit set. Note that, in practice, every bit of a tag can never be set.

A macrodot is nominally circular with a nominal diameter of ( 5/9) s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

A target is nominally circular with a nominal diameter of ( 17/9) s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

The tag pattern is allowed to vary in scale by up to ±10% according to the capabilities of the device used to produce the pattern. Any deviation from the nominal scale is recorded in the tag data to allow accurate generation of position samples.

Each symbol shown in the tag structure in FIG. 4 has a unique label. Each label consists an alphabetic prefix and a numeric suffix.

Tag Group

Tags are arranged into tag groups. Each tag group contains four tags arranged in a square. Each tag therefore has one of four possible tag types according to its location within the tag group square. The tag types are labelled 00, 10, 01 and 11, as shown in FIG. 9.

FIG. 10 shows how tag groups are repeated in a continuous tiling of tags. The tiling guarantees the any set of four adjacent tags contains one tag of each type.

Codewords

The tag contains four complete codewords. Each codeword is of a punctured 2⁴-ary (8,5) Reed-Solomon code.

Two of the codewords are unique to the tag. These are referred to as local and are labelled A and B. The tag therefore encodes up to 40 bits of information unique to the tag.

The remaining two codewords are unique to a tag type, but common to all tags of the same type within a contiguous tiling of tags. These are referred to as global and are labelled C and D, subscripted by tag type. A tag group therefore encodes up to 160 bits of information common to all tag groups within a contiguous tiling of tags.

The layout of the four codewords is shown in FIG. 11.

Reed-Solomon Encoding

Codewords are encoded using a punctured 2⁴-ary (8,5) Reed-Solomon code.

A 2⁴-ary (8,5) Reed-Solomon code encodes 20 data bits (i.e. five 4-bit symbols) and 12 redundancy bits (i.e. three 4-bit symbols) in each codeword. Its error-detecting capacity is three symbols. Its error-correcting capacity is one symbol.

As shown in FIG. 12, codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

A punctured 2⁴-ary (8,5) Reed-Solomon code is a 2⁴-ary (15,5) Reed-Solomon code with seven redundancy coordinates removed. The removed coordinates are the most significant redundancy coordinates.

The code has the following primitive polynominal: p(x)=x ⁴ +x+1

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ¹⁰)

For a detailed description of Reed-Solomon codes, refer to Wicker, S. B. and V. K. Bhargava, eds., Reed-Solomon Codes and Their Applications, IEEE Press, 1994.

Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and y respectively. When the positive x axis points to the right then the positive y axis points down.

The surface coding does not specify the location of the tag coordinate space origin on a particular tagged surface, nor the orientation of the tag coordinate space with respect to the surface. This information is application-specific. For example, if the tagged surface is a sheet of paper, then the application which prints the tags onto the paper may record the actual offset and orientation, and these can be used to normalize any digital ink subsequently captured in conjunction with the surface.

The position encoded in a tag is defined in units of tags. By convention, the position is taken to be the position of the centre of the target closest to the origin.

Tag Information Content

Table 1 defines the information fields embedded in the surface coding. Table 2 defines how these fields map to codewords.

TABLE 1 Field definitions Field width description per codeword codeword type 2 The type of the codeword, i.e. one of A (b′00′), B (b′01′), C (b′10′) and D (b′11′). per tag tag type 2 The type of the tag, i.e. one of 00 (b′00′), 01 (b′01′), 10 (b′10′) and 11 (b′11′) - corresponds to the bottom two bits of the x and y coordinates of the tag. x coordinate 13 The unsigned x coordinate of the tag allows a maximum coordinate value of approximately 14 m. y coordinate 13 The unsigned y coordinate of the tag^(b). active area flag 1 A flag indicating whether the tag is a member of an active area. b′1′ indicates membership. active area map flag 1 A flag indicating whether an active area map is present. b′1′ indicates the presence of a map (see next field). If the map is absent then the value of each map entry is derived from the active area flag (see previous field). active area map 8 A map¹ of which of the tag's immediate eight neighbours are members of an active area. b′1′ indicates membership (FIG. 13 indicates the bit ordering of the map) data fragment 8 A fragment of an embedded data stream. Only present if the active area map is absent. per tag group encoding format 8 The format of the encoding. 0: the present encoding Other values are TBA. Region flags 8 Flags controlling the interpretation and routing of region- related information. 0: region ID is an EPC 1: region is linked 2: region is interactive 3: region is signed 4: region includes data 5: region relates to mobile application Other bits are reserved and must be zero. tag size adjustment 16 The difference between the actual tag size and the nominal tag size (1.7145 mm (based on 1600 dpi, 9 dots per macrodot, and 12 macrodots per tag)), in 10 nm units, in sign-magnitude format. Region ID 96 The ID of the region containing the tags. CRC 16 A CRC of tag group data (CCITT CRC-16 (ITU, Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit, ITU-T X.25 (10/96)) Total 320

The active area map indicates whether the corresponding tags are members of an active area. An active area is an area within which any captured input should be immediately forwarded to the corresponding Hyperlabel server for interpretation. It also allows the Hyperlabel sensing device to signal to the user that the input will have an immediate effect.

TABLE 2 Mapping of fields to codewords codeword field codeword bits field Width bits A 1:0 codeword type (b′00′) 2 all 10:2  x coordinate 9 12:4  19:11 Y coordinate 9 12:4  B 1:0 codeword type (b′01′) 2 all  2 tag type 1 0 5:2 x coordinate 4 3:0  6 tag type 1 1 9:6 y coordinate 4 3:0 10 active area flag 1 all 11 active area map flag 1 all 19:12 active area map 8 all 19:12 data fragment 8 all C₀₀ 1:0 codeword type (b′10′) 2 all 9:2 encoding format 8 all 17:10 region flags 8 all 19:18 tag size adjustment 2 1:0 C₀₁ 1:0 codeword type (b′10′) 2 all 15:2  tag size adjustment 14 15:2  19:16 region ID 4 3:0 C₁₀ 1:0 codeword type (b′10′) 2 all 19:2  region ID 18 21:4  C₁₁ 1:0 codeword type (b′10′) 2 all 19:2  region ID 18 39:22 D₀₀ 1:0 codeword type (b′11′) 2 all 19:2  region ID 18 57:40 D₀₁ 1:0 codeword type (b′11′) 2 all 19:2  region ID 18 75:58 D₁₀ 1:0 codeword type (b′11′) 2 all 19:2  region ID 18 93:76 D₁₁ 1:0 codeword type (b′11′) 2 all 3:2 region ID 2 95:94 19:4  CRC 16 all

Note that the tag type can be moved into a global codeword to maximize local codeword utilization. This in turn can allow larger coordinates and/or 16-bit data fragments (potentially configurably in conjunction with coordinate precision). However, this reduces the independence of position decoding from region ID decoding and has not been included in the specification at this time.

Embedded Data

If the “region includes data” flag in the region flags is set then the surface coding contains embedded data. The data is encoded in multiple contiguous tags' data fragments, and is replicated in the surface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partial scan of the surface coding containing the embedded data can be sufficient to retrieve the entire data. The scanning system reassembles the data from retrieved fragments, and reports to the user when sufficient fragments have been retrieved without error.

As shown in Table 3, a 200-bit data block encodes 160 bits of data. The block data is encoded in the data fragments of A contiguous group of 25 tags arranged in a 5×5 square. A tag belongs to a block whose integer coordinate is the tag's coordinate divided by 5. Within each block the data is arranged into tags with increasing x coordinate within increasing y coordinate.

A data fragment may be missing from a block where an active area map is present. However, the missing data fragment is likely to be recoverable from another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of a contiguous set of blocks arranged in a rectangle. The size of the superblock is encoded in each block. A block belongs to a superblock whose integer coordinate is the block's coordinate divided by the superblock size. Within each superblock the data is arranged into blocks with increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as it will fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise type information, more precise size information, and more extensive error detection and/or correction data.

TABLE 3 Embedded data block field width description data type 8 The type of the data in the superblock. Values include: 0: type is controlled by region flags 1: MIME Other values are TBA. superblock width 8 The width of the superblock, in blocks. superblock height 8 The height of the superblock, in blocks. data 160 The block data. CRC 16 A CRC of the block data. total 200 Alternative First Example Tag Structure

Tag Group

Tags are arranged into tag groups. Each tag group contains four tags arranged in a square. Each tag therefore has one of four possible tag types according to its location within the tag group square. The tag types are labelled 00, 10, 01 and 11, as shown in FIG. 14.

Each tag in the tag group is rotated as shown in the figure, i.e. tag type 00 is rotated 0 degrees, tag type 10 is rotated 90 degrees, tag type 11 is rotated 180 degrees, and tag type 01 is rotated 270 degrees.

FIG. 15 shows how tag groups are repeated in a continuous tiling of tags. The tiling guarantees the any set of four adjacent tags contains one tag of each type.

Orientation-Indicating Cyclic Position Code

The tag contains a 2⁴-ary (4, 1) cyclic position codeword which can be decoded at any of the four possible orientations of the tag to determine the actual orientation of the tag. Symbols which are part of the cyclic position codeword have a prefix of “R” and are numbered 0 to 3 in order of increasing significance.

The cyclic position codeword is (0, 7, 9, E₁₆) Note that it only uses four distinct symbol values, even though a four-bit symbol has sixteen possible values. During decoding, any unused symbol value should, if detected, be treated as an erasure. To maximize the probability of low-weight bit error patterns causing erasures rather than symbol errors, the symbol values are chosen to be as evenly spaced on the hypercube as possible.

The minimum distance of the cyclic position code is 4, hence its error-correcting capacity is one symbol in the presence of up to one erasure, and no symbols in the presence of two or more erasures.

The layout of the orientation-indicating cyclic position codeword is shown in FIG. 16.

Local Codeword

The tag locally contains one complete codeword which is used to encode information unique to the tag. The codeword is of a punctured 2⁴-ary (13, 7) Reed-Solomon code. The tag therefore encodes up to 28 bits of information unique to the tag.

The layout of the local codeword is shown in FIG. 17.

Distributed Codewords

The tag also contains fragments of four codewords which are distributed across the four adjacent tags in a tag group and which are used to encode information common to a set of contiguous tags. Each codeword is of a 2⁴-ary (15,11) Reed-Solomon code. Any four adjacent tags therefore together encode up to 176 bits of information common to a set of contiguous tags.

The layout of the four complete codewords, distributed across the four adjacent tags in a tag group, is shown in FIG. 18. The order of the four tags in the tag group in FIG. 18 is the order of the four tags in FIG. 14.

FIG. 19 shows the layout of a complete tag group.

Reed-Solomon Encoding—Local Codeword

The local codeword is encoded using a punctured 2⁴-ary (13, 7) Reed-Solomon code. The code encodes 28 data bits (i.e. seven symbols) and 24 redundancy bits (i.e. six symbols) in each codeword. Its error-detecting capacity is six symbols. Its error-correcting capacity is three symbols.

As shown in FIG. 20, codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

The code is a 2⁴-ary (15, 7) Reed-Solomon code with two redundancy coordinates removed. The removed coordinates are the most significant redundancy coordinates.

The code has the following primitive polynominal: p(x)=x ⁴ +x+1  (EQ 1)

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ⁸)  (EQ 2)

Reed-Solomon Encoding—Distributed Codewords

The distributed codewords are encoded using a 2⁴-ary (15, 11) Reed-Solomon code. The code encodes 44 data bits (i.e. eleven symbols) and 16 redundancy bits (i.e. four symbols) in each codeword. Its error-detecting capacity is four symbols. Its error-correcting capacity is two symbols.

Codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

The code has the same primitive polynominal as the local codeword code.

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ⁴)  (EQ 3)

Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and y respectively. When the positive x axis points to the right then the positive y axis points down.

The surface coding does not specify the location of the tag coordinate space origin on a particular tagged surface, nor the orientation of the tag coordinate space with respect to the surface. This information is application-specific. For example, if the tagged surface is a sheet of paper, then the application which prints the tags onto the paper may record the actual offset and orientation, and these can be used to normalize any digital ink subsequently captured in conjunction with the surface.

The position encoded in a tag is defined in units of tags. By convention, the position is taken to be the position of the centre of the target closest to the origin.

Tag Information Content

Field Definitions

Table 4 defines the information fields embedded in the surface coding. Table 5 defines how these fields map to codewords.

TABLE 4 Field definitions width field (bits) description per tag x coordinate 9 or 13 The unsigned x coordinate of the tag allows maximum coordinate values of approximately 0.9 m and 14 m respectively. y coordinate 9 or 13 The unsigned y coordinate of the tag allows maximum coordinate values of approximately 0.9 m and 14 m respectively active area flag 1 A flag indicating whether the area (the diameter of the area, centered on the tag, is nominally 5 times the diagonal size of the tag) immediately surrounding the tag intersects an active area. b′1′ indicates intersection. data fragment flag 1 A flag indicating whether a data fragment is present (see next field). b′1′ indicates the presence of a data fragment. If the data fragment is present then the width of the x and y coordinate fields is 9. If it is absent then the width is 13. data fragment 0 or 8  A fragment of an embedded data stream. per tag group (i.e. per region) encoding format 8 The format of the encoding. 0: the present encoding Other values are reserved. region flags 8 Flags controlling the interpretation of region data. 0: region ID is an EPC 1: region has signature 2: region has embedded data 3: embedded data is signature Other bits are reserved and must be zero. tag size ID 8 The ID of the tag size. 0: the present tag size the nominal tag size is 1.7145 mm, based on 1600 dpi, 9 dots per macrodot, and 12 macrodots per tag Other values are reserved. region ID 96  The ID of the region containing the tags. signature 36  The signature of the region. high-order coordinate 4 The width of the high-order part of the x and y width (w) coordinates of the tag. high-order x coordinate 0 to 15 High-order part of the x coordinate of the tag expands the maximum coordinate values to approximately 2.4 km and 38 km respectively high-order y coordinate 0 to 15 High-order part of the y coordinate of the tag expands the maximum coordinate values to approximately 2.4 km and 38 km respectively. CRC 16  A CRC of tag group data.

An active area is an area within which any captured input should be immediately forwarded to the corresponding Hyperlabel server for interpretation. This also allows the Hyperlabel server to signal to the user that the input has had an immediate effect. Since the server has access to precise region definitions, any active area indication in the surface coding can be imprecise so long as it is inclusive.

The width of the high-order coordinate fields, if non-zero, reduces the width of the signature field by a corresponding number of bits. Full coordinates are computed by prepending each high-order coordinate field to its corresponding coordinate field.

TABLE 5 Mapping of fields to codewords codeword field codeword bits field width bits A 12:0  x coordinate 13 all 12:9  data fragment 4 3:0 25:13 y coordinate 13 all 25:22 data fragment 4 7:4 26 active area flag 1 all 27 data fragment flag 1 all B 7:0 encoding format 8 all 15:8  region flags 8 all 23:16 tag size ID 8 all 39:24 CRC 16 all 43:40 high-order coordinate 4 3:0 width (w) C 35:0  signature 36 all (35 − w):(36 − 2w) high-order x coordinate w all 35:(36 − w) high-order y coordinate w all 43:36 region ID 8 7:0 D 43:0  region ID 44 51:8  E 43:0  region ID 44 95:52

Embedded Data

If the “region has embedded data” flag in the region flags is set then the surface coding contains embedded data. The data is encoded in multiple contiguous tags' data fragments, and is replicated in the surface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partial scan of the surface coding containing the embedded data can be sufficient to retrieve the entire data. The scanning system reassembles the data from retrieved fragments, and reports to the user when sufficient fragments have been retrieved without error.

As shown in Table 6, a 200-bit data block encodes 160 bits of data. The block data is encoded in the data fragments of a contiguous group of 25 tags arranged in a 5×5 square. A tag belongs to a block whose integer coordinate is the tag's coordinate divided by 5. Within each block the data is arranged into tags with increasing x coordinate within increasing y coordinate.

A data fragment may be missing from a block where an active area map is present. However, the missing data fragment is likely to be recoverable from another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of a contiguous set of blocks arranged in a rectangle. The size of the superblock is encoded in each block. A block belongs to a superblock whose integer coordinate is the block's coordinate divided by the superblock size. Within each superblock the data is arranged into blocks with increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as it will fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise type information, more precise size information, and more extensive error detection and/or correction data.

TABLE 6 Embedded data block field width description data type 8 The type of the data in the superblock. Values include: 0: type is controlled by region flags 1: MIME Other values are TBA. superblock width 8 The width of the superblock, in blocks. superblock height 8 The height of the superblock, in blocks. data 160 The block data. CRC 16 A CRC of the block data. total 200

It will be appreciated that any form of embedded data may be used, including for example, text, image, audio, video data, such as product information, application data, contact data, business card data, and directory data.

Region Signatures

If the “region has signature” flag in the region flags is set then the signature field contains a signature with a maximum width of 36 bits. The signature is typically a random number associated with the region ID in a secure database. The signature is ideally generated using a truly random process, such as a quantum process, or by distilling randomness from random events.

In an online environment the signature can be validated, in conjunction with the region ID, by querying a server with access to the secure database.

If the “region has embedded data” and “embedded data is signature” flags in the region flags are set then the surface coding contains a 160-bit cryptographic signature of the region ID. The signature is encoded in a one-block superblock.

In an online environment any number of signature fragments can be used, in conjunction with the region ID and optionally the random signature, to validate the signature by querying a server with knowledge of the full signature or the corresponding private key.

In an offline (or online) environment the entire signature can be recovered by reading multiple tags, and can then be validated using the corresponding public signature key.

Signature verification is discussed in more detail below.

Second Example Tag Structure

FIG. 21 shows the structure of a complete tag. Each of the six black circles is a target. The tag, and the overall pattern, has six-fold rotational symmetry at the physical level.

Each diamond-shaped region represents a symbol, and each symbol represents four bits of information.

FIG. 22 shows the structure of a symbol. It contains four macrodots, each of which represents the value of one bit by its presence (one) or absence (zero).

The macrodot spacing is specified by the parameter s throughout this document. It has a nominal value of 143 μm, based on 9 dots printed at a pitch of 1600 dots per inch. However, it is allowed to vary by ±10% according to the capabilities of the device used to produce the pattern.

FIG. 23 shows an array of five adjacent symbols. The macrodot spacing is uniform both within and between symbols.

FIG. 24 shows the ordering of the bits within a symbol. Bit zero is the least significant within a symbol; bit three is the most significant. Note that this ordering is relative to the orientation of the symbol. The orientation of a particular symbol within the tag is indicated by the orientation of the label of the symbol in the tag diagrams. In general, the orientation of all symbols within a particular segment of the tag have the same orientation, consistent with the bottom of the symbol being closest to the centre of the tag.

Only the macrodots are part of the representation of a symbol in the pattern. The diamond-shaped outline of a symbol is used in this document to more clearly elucidate the structure of a tag. FIG. 25, by way of illustration, shows the actual pattern of a tag with every bit set. Note that, in practice, every bit of a tag can never be set.

A macrodot is nominally circular with a nominal diameter of ( 5/9)s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

A target is nominally circular with a nominal diameter of ( 17/9)s. However, it is allowed to vary in size by ±10% according to the capabilities of the device used to produce the pattern.

The tag pattern is allowed to vary in scale by up to ±10% according to the capabilities of the device used to produce the pattern. Any deviation from the nominal scale is recorded in the tag data to allow accurate generation of position samples.

Each symbol shown in the tag structure in FIG. 21 has a unique label. Each label consists an alphabetic prefix and a numeric suffix.

Tag Group

Tags are arranged into tag groups. Each tag group contains three tags arranged in a line. Each tag therefore has one of three possible tag types according to its location within the tag group. The tag types are labelled P, Q and R, as shown in FIG. 26.

FIG. 27 shows how tag groups are repeated in a continuous tiling of tags. The tiling guarantees the any set of three adjacent tags contains one tag of each type.

Orientation-Indicating Cyclic Position Code

The tag contains a 2³-ary (6,1) cyclic position codeword (this work is currently the subject of two pending U.S. patent applications, entitled “Cyclic position codes” and “Orientation indicating cyclic position codes” with application Ser. Nos. 10/120,441 and 10/409,864, respectively) which can be decoded at any of the six possible orientations of the tag to determine the actual orientation of the tag. Symbols which are part of the cyclic position codeword have a prefix of “R” and are numbered 0 to 5 in order of increasing significance.

The layout of the orientation-indicating cyclic position codeword is shown in FIG. 28.

The cyclic position codeword is (0,5,6,9,A₁₆,F₁₆). Note that it only uses six distinct symbol values, even though a four-bit symbol has sixteen possible values. During decoding, any unused symbol value should, if detected, be treated as an erasure. To maximize the probability of low-weight bit error patterns causing erasures rather than symbol errors, the symbol values are chosen to be evenly-spaced on the hypercube.

The minimum distance of the cyclic position code is 6, hence its error-correcting capacity is two symbols in the presence of up to one erasure, one symbol in the presence of two or three erasures, and no symbols in the presence of four or more erasures.

Local Codeword

The tag locally contains one complete codeword, labelled A, which is used to encode information unique to the tag. The codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. The tag therefore encodes up to 28 bits of information unique to the tag.

The layout of the local codeword is shown in FIG. 29.

Distributed Codewords

The tag also contains fragments of six codewords, labelled B through G, which are distributed across three adjacent tags and which are used to encode information common to a set of contiguous tags. Each codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. Any three adjacent tags therefore together encode up to 168 bits of information common to a set of contiguous tags.

The layout of the first four fragments of the six codewords B through G in tag type P is shown in FIG. 30. The layout in the other tag types follows the layout in tag type P, with symbols 4 through 7 in tag type Q, and fragments 8 through 11 in tag type Q.

The layout of the six complete codewords B through G, distributed across the three tag types P, Q and R, is shown in FIG. 31.

As shown earlier in FIG. 27, the tiling guarantees the any set of three adjacent tags contains one tag of each type, and therefore contains a complete set of distributed codewords. The tag type, used to determine the registration of the distributed codewords with respect to a particular set of adjacent tags, is inferred from the x-y coordinate encoded in the local codeword of each tag.

Tag Segment Geometry

FIG. 32 shows the geometry of a tag segment.

FIG. 33 shows the spacing d between tag segments, required to maintain consistent spacing between macrodots, where d is given by: d=(1−√{square root over (3)}/3)s

FIG. 34 shows the effect of the inter-segment spacing d on target position. Compared with their nominal positions in relation to closely-packed segments (i.e. with d=0), diagonal targets must be displaced by (Δ_(x),Δ_(y))=(±1/√{square root over (3)}, ±1)d, and horizontal targets must be displaced by (Δ_(x), Δ_(y))=(±2/√{square root over (3)}, 0)d.

Reed-Solomon Encoding

Codewords are encoded using a punctured 2⁴-ary (12,7) Reed-Solomon code.

A 2⁴-ary (12,7) Reed-Solomon code encodes 28 data bits (i.e. seven 4-bit symbols) and 20 redundancy bits (i.e. five 4-bit symbols) in each codeword. Its error-detecting capacity is five symbols. Its error-correcting capacity is two symbols.

As shown in FIG. 35, codeword coordinates are indexed in coefficient order, and the data bit ordering follows the codeword bit ordering.

A punctured 2⁴-ary (12,7) Reed-Solomon code is a 2⁴-ary (15,7) Reed-Solomon code with three redundancy coordinates removed. The removed coordinates are the most significant redundancy coordinates.

The code has the following primitive polynominal: p(x)=x ⁴ +x+1

The code has the following generator polynominal: g(x)=(x+α)(x+α ²) . . . (x+α ⁸)

For a detailed description of Reed-Solomon codes, refer to Wicker, S. B. and V. K. Bhargava, eds., Reed-Solomon Codes and Their Applications, IEEE Press, 1994.

Tag Coordinate Space

The tag coordinate space has two orthogonal axes labelled x and y respectively. When the positive x axis points to the right then the positive y axis points down.

The surface coding does not specify the location of the tag coordinate space origin on a particular tagged surface, nor the orientation of the tag coordinate space with respect to the surface. This information is application-specific. For example, if the tagged surface is a sheet of paper, then the application which prints the tags onto the paper may record the actual offset and orientation, and these can be used to normalize any digital ink subsequently captured in conjunction with the surface.

The position encoded in a tag is defined in units of tags. Tag coordinates are arranged as shown in in FIG. 36, where the tag with coordinate (0,0) is a P type tag. By convention, the position of a tag with an even y coordinate is defined to be the position of the center of the tag. The position of a tag with an odd y coordinate is therefore defined to be the position of the midpoint between the center of the tag and the center of its neighboring tag on the left.

Horizontal and vertical tag units, based on center-to-center tag tag spacings, are given by:

$u_{x} = {{{4\left( {2\sqrt{3}s} \right)} + {2d}} \cong {14.1s}}$ $u_{y} = {{{6\left( {2s} \right)} + {2\left( {d\frac{\sqrt{3}}{2}} \right)}} \cong {12.2s}}$ where d is the inter-segment spacing given by d=(1−√{square root over (3)}/2)s

If the three tag types P, Q and R are assigned values 0, 1 and 2 respectively, then the type ^(t) of a tag is inferred from its (x,y) coordinate as follows. If y is even, then: t=x modulo 3 if y is odd, then: t=(x−1)modulo 3

Tag Information Content

Table 7 defines the information fields embedded in the surface coding. Table 8 defines how these fields map to codewords.

TABLE 7 Field Definitions field width description per tag X coordinate 10 The unsigned x coordinate of the tag allows a maximum x coordinate value of approximately 2.1 m (based on EQ 4). Y coordinate 10 The unsigned y coordinate of the tag allows a maximum y coordinate value of approximately 1.8 m (based on EQ 5. active area flag 1 A flag indicating whether the tag is a member of an active area. b′1′ indicates membership. active area map flag 1 A flag indicating whether an active area map is present. b′1′ indicates the presence of a map (see next field). If the map is absent then the value of each map entry is derived from the active area flag (see previous field). active area map 6 A map of which of the tag's immediate six neighbours are members of an active area. b′1′ indicates membership - FIG. 37 indicates the bit ordering of the map data fragment 6 A fragment of an embedded data stream. Only present if the active area map is absent. per tag group encoding format 12 The format of the encoding. 0: the present encoding Other values are TBA. macrodot spacing adjustment 16 The difference between the actual macrodot spacing and the nominal macrodot spacing, in nm units, in sign-magnitude format - the nominal macrodot spacing is 142875 nm (based on 1600 dpi and 9 dots per macrodot) region flags 12 Flags controlling the interpretation and routing of region-related information. 0: region ID is an EPC 1: region is linked 2: region is interactive 3: region is signed 4: region includes data 5: region relates to mobile application Other bits are reserved and must be zero. region ID 112 The ID of the region containing the tags. CRC 16 A CRC (CCITT CRC-16) of tag group data.

The active area map indicates whether the corresponding tags are members of an active area. An active area is an area within which any captured input should be immediately forwarded to the corresponding Hyperlabel server for interpretation. It also allows the Hyperlabel sensing device to signal to the user that the input will have an immediate effect.

TABLE 8 Mapping of fields to codewords codeword field field codeword bits width bits field A 9:0 10 all x coordinate 19:10 10 all y coordinate 20 1 all active area flag 21 1 all active area map flag 27:22 6 all active area map 27:22 6 all data fragment B 11:0 12 all Encoding format 27:12 16 all Macrodot spacing adjustment C 11:0  12 all region flags 27:12 16 27:12 region ID D 27:0  28 55:28 E 27:0  28 83:56 F 27:0  28 111:84  G 11:0  12 11:0  27:12 16 all CRC

Embedded Data

If the “region includes data” flag in the region flags is set then the surface coding contains embedded data. The data is encoded in multiple contiguous tags' data fragments, and is replicated in the surface coding as many times as it will fit.

The embedded data is encoded in such a way that a random and partial scan of the surface coding containing the embedded data can be sufficient to retrieve the entire data. The scanning system reassembles the data from retrieved fragments, and reports to the user when sufficient fragments have been retrieved without error.

As shown in Table 9, a 216-bit data block encodes 160 bits of data.

TABLE 9 Embedded data block field width Description data type 16 The type of the data in the superblock.Values include: 0: type is controlled by region flags 1: MIME Other values are TBA. superblock width 12 The width of the superblock, in blocks. superblock height 12 The height of the superblock, in blocks. data 160 The block data. CRC 16 A CRC of the block data. total 216

The block data is encoded in the data fragments of a contiguous group of 36 tags arranged in a 6×6 square as shown in FIG. 38. A tag belongs to a block whose integer x and y coordinates are the tag's x and y coordinates divided by 6. Within each block the data is arranged into tags with increasing x coordinate within increasing y coordinate.

A data fragment may be missing from a block where an active area map is present. However, the missing data fragment is likely to be recoverable from another copy of the block.

Data of arbitrary size is encoded into a superblock consisting of a contiguous set of blocks arranged in a rectangle. The size of the superblock is encoded in each block. A block belongs to a superblock whose integer coordinate is the block's coordinate divided by the superblock size. Within each superblock the data is arranged into blocks with increasing x coordinate within increasing y coordinate.

The superblock is replicated in the surface coding as many times as it will fit, including partially along the edges of the surface coding.

The data encoded in the superblock may include more precise type information, more precise size information, and more extensive error detection and/or correction data.

General Considerations

Cryptographic Signature of Region ID

If the “region is signed” flag in the region flags is set then the surface coding contains a 160-bit cryptographic signature of the region ID. The signature is encoded in a one-block superblock.

In an online environment any signature fragment can be used, in conjunction with the region ID, to validate the signature. In an offline environment the entire signature can be recovered by reading multiple tags, and can then be validated using the corresponding public signature key.

MIME Data

If the embedded data type is “MIME” then the superblock contains Multipurpose Internet Mail Extensions (MIME) data according to RFC 2045 (Freed, N., and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME)—Part One: Format of Internet Message Bodies”, RFC 2045, November 1996), RFC 2046 (Freed, N., and N. Borenstein, “Multipurpose Internet Mail Extensions (MIME)—Part Two: Media Types”, RFC 2046, November 1996) and related RFCs. The MIME data consists of a header followed by a body. The header is encoded as a variable-length text string preceded by an 8-bit string length. The body is encoded as a variable-length type-specific octet stream preceded by a 16-bit size in big-endian format.

The basic top-level media types described in RFC 2046 include text, image, audio, video and application.

RFC 2425 (Howes, T., M. Smith and F. Dawson, “A MIME Content-Type for Directory Information”, RFC 2045, September 1998) and RFC 2426 (Dawson, F., and T. Howes, “vCard MIME Directory Profile”, RFC 2046, September 1998) describe a text subtype for directory information suitable, for example, for encoding contact information which might appear on a business card.

Encoding and Printing Considerations

The Print Engine Controller (PEC) (which is the subject of a number of pending U.S. patent applications, including: Ser. Nos. 09/575,108; 10/727,162; 09/575,110; 09/607,985; U.S. Pat. Nos. 6,398,332; 6,394,573; 6,622,923) supports the encoding of two fixed (per-page) 2⁴-ary (15,7) Reed-Solomon codewords and four variable (per-tag) 2⁴-ary (15,7) Reed-Solomon codewords, although other numbers of codewords can be used for different schemes.

Furthermore, PEC supports the rendering of tags via a rectangular unit cell whose layout is constant (per page) but whose variable codeword data may vary from one unit cell to the next. PEC does not allow unit cells to overlap in the direction of page movement.

A unit cell compatible with PEC contains a single tag group consisting of four tags. The tag group contains a single A codeword unique to the tag group but replicated four times within the tag group, and four unique B codewords. These can be encoded using five of PEC's six supported variable codewords. The tag group also contains eight fixed C and D codewords. One of these can be encoded using the remaining one of PEC's variable codewords, two more can be encoded using PEC's two fixed codewords, and the remaining five can be encoded and pre-rendered into the Tag Format Structure (TFS) supplied to PEC.

PEC imposes a limit of 32 unique bit addresses per TFS row. The contents of the unit cell respect this limit. PEC also imposes a limit of 384 on the width of the TFS. The contents of the unit cell respect this limit.

Note that for a reasonable page size, the number of variable coordinate bits in the A codeword is modest, making encoding via a lookup table tractable. Encoding of the B codeword via a lookup table may also be possible. Note that since a Reed-Solomon code is systematic, only the redundancy data needs to appear in the lookup table.

Imaging and Decoding Considerations

The minimum imaging field of view required to guarantee acquisition of an entire tag has a diameter of 39.6 s, i.e. (2×(12+2))√{square root over (2)}s allowing for arbitrary alignment between the surface coding and the field of view. Given a macrodot spacing of 143 μm, this gives a required field of view of 5.7 mm.

Table 10 gives pitch ranges achievable for the present surface coding for different sampling rates, assuming an image sensor size of 128 pixels.

TABLE 10 Pitch ranges achievable for present surface coding for different sampling rates, computed using Optimize Hyperlabel Optics; dot pitch = 1600 dpi, macrodot pitch = 9 dots, viewing distance = 30 mm, nib-to-FOV separation = 1 mm, image sensor size = 128 pixels sampling rate pitch range 2 −40 to

49 2.5 −27 to

36 3 −10 to

18

For the surface coding of the first example, the corresponding decoding sequence is as follows:

-   -   locate targets of complete tag     -   infer perspective transform from targets     -   sample and decode any one of tag's four codewords     -   determine codeword type and hence tag orientation     -   sample and decode required local (A and B) codewords     -   codeword redundancy is only 12 bits, so only detect errors     -   on decode error flag bad position sample     -   determine tag x-y location, with reference to tag orientation     -   infer 3D tag transform from oriented targets     -   determine nib x-y location from tag x-y location and 3D         transform     -   determine active area status of nib location with reference to         active area map     -   generate local feedback based on nib active area status     -   determine tag type from A codeword     -   sample and decode required global (C and D) codewords (modulo         window alignment, with reference to tag type)     -   although codeword redundancy is only 12 bits, correct errors;         subsequent CRC verification will detect erroneous error         correction     -   verify tag group data CRC     -   on decode error flag bad region ID sample     -   determine encoding type, and reject unknown encoding     -   determine region flags     -   determine region ID     -   encode region ID, nib x-y location, nib active area status in         digital ink     -   route digital ink based on region flags

Note that region ID decoding need not occur at the same rate as position decoding.

Note that decoding of a codeword can be avoided if the codeword is found to be identical to an already-known good codeword.

For the surface coding of the alternative first example, the corresponding decoding sequence is as follows:

-   -   locate targets of complete tag     -   infer perspective transform from targets     -   sample cyclic position code     -   decode cyclic position code     -   determine orientation from cyclic position code     -   sample and decode local Reed-Solomon codeword     -   determine tag x-y location     -   infer 3D tag transform from oriented targets     -   determine nib x-y location from tag x-y location and 3D         transform     -   determine active area status of nib location with reference to         active area map     -   generate local feedback based on nib active area status     -   determine tag type     -   sample distributed Reed-Solomon codewords (modulo window         alignment, with reference to tag type)     -   decode distributed Reed-Solomon codewords     -   verify tag group data CRC     -   on decode error flag bad region ID sample     -   determine encoding type, and reject unknown encoding     -   determine region flags     -   determine region ID     -   encode region ID, nib x-y location, nib active area status in         digital ink     -   route digital ink based on region flags

Region ID decoding need not occur at the same rate as position decoding and decoding of a codeword can be avoided if the codeword is found to be identical to an already-known good codeword.

If the high-order coordinate width is non-zero, then special care must be taken on boundaries between tags where the low-order x or y coordinate wraps, otherwise codeword errors may be introduced. If wrapping is detected from the low-order x or y coordinate (i.e. it contains all zero bits or all one bits), then the corresponding high-order coordinate can be adjusted before codeword decoding. In the absence of genuine symbol errors in the high-order coordinate, this will prevent the inadvertent introduction of codeword errors.

Expanded Tag

The tag can be expanded to increase its data capacity by adding additional bands of symbols about its circumference. This appendix describes an expanded tag with one additional band of symbols. While the tag described in the main part of the document has a raw capacity of 36 symbols, the expanded tag has a raw capacity of 60 symbols.

The capacity of the expanded tag is precisely sufficient to allow the inclusion of a complete 160-bit digital signature in each tag group. This allows complete digital signature verification on a “single-click” interaction with the surface coding.

Tag Structure

FIG. 39 shows the structure of a complete (P type) expanded tag. Apart from the additional band of symbols and the related change in the positions of the targets, it has a similar physical structure to the tag described earlier.

In the expanded tag the macrodot spacing s has a nominal value of 111 μm, based on 7 dots printed at a pitch of 1600 dots per inch.

A macrodot is nominally circular with a nominal diameter of ( 3/7)s.

A target is nominally circular with a nominal diameter of ( 10/7)s.

The expanded tag, like the tag described earlier, also participates in a tag group, and each expanded tag has one of the three possible tag types P, Q and R.

The expanded tag, like the tag described earlier, contains an orientation-indicating cyclic position code.

Local Codeword

The expanded tag locally contains one complete codeword which is used to encode information unique to the tag. The codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. The tag therefore encodes up to 28 bits of information unique to the tag.

The layout of the local codeword is shown in FIG. 40.

Distributed Codewords

The expanded tag contains fragments of twelve codewords, labelled B through M, which are distributed across three adjacent tags and which are used to encode information common to a set of contiguous tags. Each codeword is of a punctured 2⁴-ary (12,7) Reed-Solomon code. Any three adjacent tags therefore together encode up to 336 bits of information common to a set of contiguous tags.

The layout of the first four fragments of the six codewords B through G in tag type P is shown in FIG. 41. The layout in the other tag types follows the layout in tag type P, with symbols 4 through 7 in tag type Q, and fragments 8 through 11 in tag type Q.

The layout of the first four fragments of the six codewords H through M in tag type P is shown in FIG. 42. The layout in the other tag types follows the layout in tag type P, with symbols 4 through 7 in tag type Q, and fragments 8 through 11 in tag type Q.

As shown earlier in FIG. 37, the tiling guarantees the any set of three adjacent tags contains one tag of each type, and therefore contains a complete set of distributed codewords. The tag type, used to determine the registration of the distributed codewords with respect to a particular set of adjacent tags, is inferred from the x-y coordinate encoded in the local codeword of each tag.

Tag Coordinate Space

The tag coordinate space encoded in the expanded tag is identical to that encoded in the tag described earlier, with the exception that tag units are different (due both to the change in tag structure and the change in macrodot spacing).

Horizontal and vertical tag units, based on center-to-center tag tag spacings, are given by:

$u_{x} = {{{5\left( {2\sqrt{3}s} \right)} + {2\; d}} \cong {17.6s}}$ $u_{y} = {{{7.5\left( {2s} \right)} + {2\left( {d\frac{\sqrt{3}}{2}} \right)}} \cong {15.2\; s}}$ where d is the inter-segment spacing given by d=(1−√{square root over (3)}/2)s

Tag Information Content

Table 11 defines the information fields embedded in the expanded tag surface coding. Table 12 defines how these fields map to codewords.

TABLE 11 Field definitions Field width description per tag x coordinate 10 The unsigned x coordinate of the tag - allows a maximum x coordinate value of approximately 2.0 m (based on EQ 8). y coordinate 10 The unsigned y coordinate of the tag - allows a maximum y coordinate value of approximately 1.7 m (based on EQ 9) active area 1 A flag indicating whether the tag is a member of flag an active area, b′1′ indicates membership. active area 1 A flag indicating whether an active area map is map flag present. b′1′ indicates the presence of a map (see next field). If the map is absent then the value of each map entry is derived from the active area flag (see previous field). active area 6 A map of which of the tag's immediate six map neighbours are members of an active area. b′1′ indicates membership - FIG. 37 indicates the bit ordering of the map data 6 A fragment of an embedded data stream. Only fragment present if the active area map is absent. per tag group encoding 12 The format of the encoding. format Refer to Table 5 for values. macrodot 16 The difference between the actual macrodot spacing spacing and the nominal macrodot spacing, in adjustment nm units, in sign-magnitude format - the nominal macrodot spacing is 111125 nm (based on 1600 dpi and 7 dots per macrodot region 12 Flags controlling the interpretation and flags routing of region-related information. Refer to Table 5 for values. region ID 112 The ID of the region containing the tags. Signature 160 A digital signature of the region ID. CRC 16 A CRC (CCITT CRC-16) of tag group data.

TABLE 12 Mapping of fields to codewords codeword field field codeword bits width bits field A  9:0 10 all x coordinate  19:10 10 all y coordinate 20 1 all active area flag 21 1 all active area map flag  27:22 6 all active area map  27:22 6 all data fragment B 11:0 12 all encoding format  27:12 16 all macrodot spacing adjustment C 11:0 12 all region flags  27:12 16 27:12 region ID D 27:0 28 55:28 E 27:0 28 83:56 F 27:0 28 111:84  G 11:0 12 11:0   27:12 16 all CRC H 27:0 28 27:0  signature I 27:0 28 55:28 J 27:0 28 83:56 K 27:0 28 111:84  L 27:0 28 139:112 M 19:0 20 159:140  27:20 8 all unused

Encoding and Printing Considerations

The tag group unit cell of the expanded tag only respects PEC's TFS width limit if the macrodot spacing is reduced from 9 to 7 dots, as reflected in the macrodot spacing s of 111 μm.

Imaging and Decoding Considerations

The minimum imaging field of view required to guarantee acquisition of an entire expanded tag has a diameter of 44 s i.e. 2(1+8+2)2s), allowing for arbitrary alignment between the surface coding and the field of view. Given a macrodot spacing of 111 μm this gives a required field of view of approximately 4.0 mm. Surface Coding Security

Security Requirements

Item security can be defined to have two related purposes:

-   -   to allow authentication of an item     -   to prevent forgery of an item

The greater the difficulty of forgery, the greater the trustworthiness of authentication. When an item is coded, Hyperlabel surface coding security has two corresponding purposes:

-   -   to allow authentication of a coded item     -   to prevent forgery of a coded item with a novel item ID

If a user is able to determine the authenticity of the surface coding of an item, then the user may be able to make an informed decision about the likely authenticity of the item.

If it is intractable to forge the surface coding for a novel ID, then the only tractable way of forging an item with an authentic surface coding is to duplicate the surface coding of an existing item (and hence its ID). If the user is able to determine by other means that the ID of an item is likely to be unique, then the user may assume that the item is authentic.

Since the Hyperlabel surface coding allows meaningful interaction between a sensing device and a coded surface during a purely local interaction, it is desirable for the surface coding to support authentication during a similarly local interaction, i.e. without requiring an increase in the size of the sensing device field of view.

Since no a priori relationship exists between creators of authentic coded items and users potentially wishing to authenticate such items, it is undesirable to require a trust relationship between creators and users. For example, it is undesirable to require that creators share secret signature keys with users.

It is reasonable for many users to rely on online access to an authenticator trusted by a creator for the purposes of authenticating items. Conversely, it is desirable to allow authentication to take place in the absence of online access.

Security Discussion

As described above, authentication relies on verifying the correspondence between data and a signature of that data. The greater the difficulty in forging a signature, the greater the trustworthiness of signature-based authentication.

The item ID is unique and therefore provides a basis for a signature. If online authentication access is assumed, then the signature may simply be a random number associated with the item ID in an authentication database accessible to the trusted online authenticator. The random number may be generated by any suitable method, such as via a deterministic (pseudo-random) algorithm, or via a stochastic physical process. A keyed hash or encrypted hash may be preferable to a random number since it requires no additional space in the authentication database. However, a random signature of the same length as a keyed signature is more secure than the keyed signature since it is not susceptible to key attacks. Equivalently, a shorter random signature confers the same security as a longer keyed signature.

In the limit case no signature is actually required, since the mere presence of the item ID in the database indicates authenticity. However, the use of a signature limits a forger to forging items he has actually sighted.

To prevent forgery of a signature for an unsighted ID, the signature must be large enough to make exhaustive search via repeated accesses to the online authenticator intractable. If the signature is generated using a key rather than randomly, then its length must also be large enough to prevent the forger from deducing the key from known ID-signature pairs. Signatures of a few hundred bits are considered secure, whether generated using private or secret keys.

While it may be practical to include a reasonably secure random signature in a tag (or local tag group), particularly if the length of the ID is reduced to provide more space for the signature, it may be impractical to include a secure ID-derived signature in a tag. To support a secure ID-derived signature, we can instead distribute fragments of the signature across multiple tags. If each fragment can be verified in isolation against the ID, then the goal of supporting authentication without increasing the sensing device field of view is achieved. The security of the signature can still derive from the full length of the signature rather than from the length of a fragment, since a forger cannot predict which fragment a user will randomly choose to verify. A trusted authenticator can always perform fragment verification since they have access to the key and/or the full stored signature, so fragment verification is always possible when online access to a trusted authenticator is available.

Fragment verification requires that we prevent brute force attacks on individual fragments, otherwise a forger can determine the entire signature by attacking each fragment in turn. A brute force attack can be prevented by throttling the authenticator on a per-ID basis. However, if fragments are short, then extreme throttling is required. As an alternative to throttling the authenticator, the authenticator can instead enforce a limit on the number of verification requests it is willing to respond to for a given fragment number. Even if the limit is made quite small, it is unlikely that a normal user will exhaust it for a given fragment, since there will be many fragments available and the actual fragment chosen by the user can vary. Even a limit of one can be practical. More generally, the limit should be proportional to the size of the fragment, i.e. the smaller the fragment the smaller the limit. Thus the experience of the user would be somewhat invariant of fragment size. Both throttling and enforcing fragment verification limits imply serialization of requests to the authenticator. A fragment verification limit need only be imposed once verification fails, i.e. an unlimited number of successful verifications can occur before the first failure. Enforcing fragment verification limits further requires the authenticator to maintain a per-fragment count of satisfied verification requests.

A brute force attack can also be prevented by concatenating the fragment with a random signature encoded in the tag. While the random signature can be thought of as protecting the fragment, the fragment can also be thought of as simply increasing the length of the random signature and hence increasing its security. A fragment verification limit can make verification subject to a denial of service attack, where an attacker deliberately exceeds the limit with invalid verification request in order to prevent further verification of the item ID in question. This can be prevented by only enforcing the fragment verification limit for a fragment when the accompanying random signature is correct.

Fragment verification may be made more secure by requiring the verification of a minimum number of fragments simultaneously.

Fragment verification requires fragment identification. Fragments may be explicitly numbered, or may more economically be identified by the two-dimensional coordinate of their tag, modulo the repetition of the signature across a continuous tiling of tags.

The limited length of the ID itself introduces a further vulnerability. Ideally it should be at least a few hundred bits. In the netpage surface coding scheme it is 96 bits or less. To overcome this the ID may be padded. For this to be effective the padding must be variable, i.e. it must vary from one ID to the next. Ideally the padding is simply a random number, and must then be stored in the authentication database indexed by ID. If the padding is deterministically generated from the ID then it is worthless.

Offline authentication of secret-key signatures requires the use of a trusted offline authentication device. The QA integrated circuit (which is the subject of a number of pending U.S. patent applications, including Ser. Nos. 09/112,763; 09/112,762; 09/112,737; 09/112,761; 09/113,223) provides the basis for such a device, although of limited capacity. The QA integrated circuit can be programmed to verify a signature using a secret key securely held in its internal memory. In this scenario, however, it is impractical to support per-ID padding, and it is impractical even to support more than a very few secret keys. Furthermore, a QA integrated circuit programmed in this manner is susceptible to a chosen-message attack. These constraints limit the applicability of a QA-integrated circuit-based trusted offline authentication device to niche applications.

In general, despite the claimed security of any particular trusted offline authentication device, creators of secure items are likely to be reluctant to entrust their secret signature keys to such devices, and this is again likely to limit the applicability of such devices to niche applications.

By contrast, offline authentication of public-key signatures (i.e. generated using the corresponding private keys) is highly practical. An offline authentication device utilizing public keys can trivially hold any number of public keys, and may be designed to retrieve additional public keys on demand, via a transient online connection, when it encounters an ID for which it knows it has no corresponding public signature key. Untrusted offline authentication is likely to be attractive to most creators of secure items, since they are able to retain exclusive control of their private signature keys.

A disadvantage of offline authentication of a public-key signature is that the entire signature must be acquired from the coding, violating our desire to support authentication with a minimal field of view. A corresponding advantage of offline authentication of a public-key signature is that access to the ID padding is no longer required, since decryption of the signature using the public signature key generates both the ID and its padding, and the padding can then be ignored. A forger can not take advantage of the fact that the padding is ignored during offline authentication, since the padding is not ignored during online authentication.

Acquisition of an entire distributed signature is not particularly onerous. Any random or linear swipe of a hand-held sensing device across a coded surface allows it to quickly acquire all of the fragments of the signature. The sensing device can easily be programmed to signal the user when it has acquired a full set of fragments and has completed authentication. A scanning laser can also easily acquire all of the fragments of the signature. Both kinds of devices may be programmed to only perform authentication when the tags indicate the presence of a signature.

Note that a public-key signature may be authenticated online via any of its fragments in the same way as any signature, whether generated randomly or using a secret key. The trusted online authenticator may generate the signature on demand using the private key and ID padding, or may store the signature explicitly in the authentication database. The latter approach obviates the need to store the ID padding.

Note also that signature-based authentication may be used in place of fragment-based authentication even when online access to a trusted authenticator is available.

Table 13 provides a summary of which signature schemes are workable in light of the foregoing discussion.

TABLE 13 Summary of workable signature schemes online encoding acquisition signature authen- offline in tags from tags generation tication authentication Local full random ok Impractical to store per ID information secret key Signature Undesirable to too short store secret keys to be secure private key Signature too short to be secure Distri- fragment(s) random ok impractical^(b) buted secret key ok impractical^(c) private key ok impractical^(b) full random ok impractical^(b) secret key ok impractical^(c) private key ok ok

Security Specification

FIG. 43 shows an example item signature object model.

An item has an ID (X) and other details (not shown). It optionally has a secret signature (Z). It also optionally has a public-key signature. The public-key signature records the signature (S) explicitly, and/or records the padding (P) used in conjunction with the ID to generate the signature. The public-key signature has an associated public-private key pair (K, L). The key pair is associated with a one or more ranges of item IDs.

Typically issuers of security documents and pharmaceuticals will utilize a range of IDs to identify a range of documents or the like. Following this, the issuer will then use these details to generate respective IDs for each item, or document to be marked.

Authentication of the product can then be performed online or offline by sensing the tag data encoded within the tag, and performing the authentication using a number of different mechanisms depending on the situation.

Examples of the processes involved will now be described for public and private key encryption respectively.

Authentication Based on Public-Key Signature

Setup per ID range:

-   -   generate public-private signature key pair (K, L)     -   store key pair (K, L) indexed by ID range

Setup per ID:

-   -   generate ID padding (P)     -   retrieve private signature key (L) by ID (X)     -   generate signature (S) by encrypting ID (X) and padding (P)         using private key (L):         S←E_(L)(X, P)     -   store signature (S) in database indexed by ID (X) (and/or store         padding (P))     -   encode ID (X) in all tag groups     -   encode signature (S) across multiple tags in repeated fashion

Online fragment-based authentication (user):

-   -   acquire ID (X) from tags     -   acquire position (x, y)_(i) and signature fragment (T_(i)) from         tag generate fragment number (i) from position (x, y)_(i):         i←F[(x, y)_(i)]     -   look up trusted authenticator by ID (X)     -   transmit ID (X), fragment (T_(i)) and fragment number (i) to         trusted authenticator

Online fragment-based authentication (trusted authenticator):

-   -   receive ID (X), fragment (T_(i)) and fragment number (i) from         user     -   retrieve signature (S) from database by ID (X) (or re-generate         signature)     -   compare received fragment (T_(i)) with corresponding fragment of         signature (S_(i))     -   report authentication result to user

Offline signature-based authentication (user):

-   -   acquire ID from tags (X)     -   acquire positions (x, y)_(i) and signature fragments (T_(i))         from tag     -   generate fragment numbers (i) from positions (x, y)_(i):         i←F[(x, y)_(i)]     -   generate signature (i) from (n) fragments:         T←T₀|T₁|. . . |T_(n−1)     -   retrieve public signature key (K) by ID (X)     -   decrypt signature (T) using public key (K) to obtain ID (X′) and         padding (P′):         X′|P′←D_(K)(T)     -   compare acquired ID (X) with decrypted ID (X′)     -   report authentication result to user

Authentication Based on Secret-Key Signature

Setup per ID:

-   -   generate secret (Z)     -   store secret (Z) in database indexed by ID (X)     -   encode ID (X) and secret (Z) in all tag groups

Online secret-based authentication (user):

-   -   acquire ID (X) from tags     -   acquire secret (Z′) from tags     -   look up trusted authenticator by ID     -   transmit ID (X) and secret (Z′) to trusted authenticator

Online secret-based authentication (trusted authenticator):

-   -   receive ID (X) and secret (Z′) from user     -   retrieve secret (Z) from database by ID (X)     -   compared received secret (Z′) with secret (Z)     -   report authentication result to user

As discussed earlier, secret-based authentication may be used in conjunction with fragment-based authentication.

Cryptographic Algorithms

When the public-key signature is authenticated offline, the user's authentication device typically does not have access to the padding used when the signature was originally generated. The signature verification step must therefore decrypt the signature to allow the authentication device to compare the ID in the signature with the ID acquired from the tags. This precludes the use of algorithms which don't perform the signature verification step by decrypting the signature, such as the standard Digital Signature Algorithm U.S. Department of Commerce/National Institute of Standards and Technology, Digital Signature Standard (DSS), FIPS 186-2, 27 Jan. 2000.

RSA encryption is described in:

-   -   Rivest, R. L., A. Shamir, and L. Adleman, “A Method for         Obtaining Digital Signatures and Public-Key Cryptosystems”,         Communications of the ACM, Vol. 21, No. 2, February 1978, pp.         120-126     -   Rivest, R. L., A. Shamir, and L. M. Adleman, “Cryptographic         communications system and method”, U.S. Pat. No. 4,405,829,         issued 20 Sep. 1983     -   RSA Laboratories, PKCS #1 v2.0: RSA Encryption Standard, Oct. 1,         1998

RSA provides a suitable public-key digital signature algorithm that decrypts the signature. RSA provides the basis for the ANSI X9.31 digital signature standard American National Standards Institute, ANSI X9.31-1998, Digital Signatures Using Reversible Public Key Cryptography for the Financial Services Industry (rDSA), Sep. 8, 1998. If no padding is used, then any public-key signature algorithm can be used.

In the Hyperlabel surface coding scheme the ID is 96 bits long or less. It is padded to 160 bits prior to being signed.

The padding is ideally generated using a truly random process, such as a quantum process [14,15], or by distilling randomness from random events Schneier, B., Applied Cryptography, Second Edition, John Wiley & Sons 1996.

In the Hyperlabel surface coding scheme the random signature, or secret, is 36 bits long or less. It is also ideally generated using a truly random process. If a longer random signature is required, then the length of the item ID in the surface coding can be reduced to provide additional space for the signature.

Security Tagging and Tracking

Currency, checks and other monetary documents can be tagged in order to detect currency counterfeiting and counter money laundering activities. The Hyperlabel tagged currency can be validated, and tracked through the monetary system. Hyperlabel tagged products such as pharmaceuticals can be tagged allowing items to be validated and tracked through the distribution and retail system.

A number of examples of the concepts of Hyperlabel security tagging and tracking referring specifically to bank notes and pharmaceuticals, however Hyperlabel tagging can equally be used to securely tag and track other products, for example, traveller's checks, demand deposits, passports, chemicals etc.

Hyperlabel tagging, with the netpage system, provides a mechanism for securely validating and tracking objects.

Hyperlabel tags on the surface of an object uniquely identify the object. Each Hyperlabel tag contains information including the object's unique ID, and the tag's location on the Hyperlabel tagged surface. A Hyperlabel tag also contains a signature fragment which can be used to authenticate the object. A scanning laser or image sensor can read the tags on any part of the object to identify the object, validate the object, and allow tracking of the object.

Currency Tagging

Currency may be tagged with Hyperlabels in order to detect counterfeiting and allow tracking of currency movement. Hyperlabel tags can be printed over the entire bank note surface or can be printed in a smaller region of the note. Hyperlabel tagging can be used in addition to other security features such as holograms, foil strips, colour-shifting inks etc. A scanning laser or image sensor can read the tags on any part of the note to validate each individual note.

A Hyperlabel currency tag identifies the note currency, issue country, and note denomination. It also identifies the note's serial number, the note side (i.e. front or back), and it may contain other information (for example, the exact printing works where the note was printed). There are two note IDs for each physical bank note—one for each side of the note.

Each time a note is scanned its location is recorded. This location information can be collected in a central database allowing analysis and identification of abnormal money movements and detection of counterfeit notes. For example, in the case of sophisticated forgeries where Hyperlabel dot patterns are exactly duplicated, there will be multiple copies of exactly forged notes (at a minimum, the original and the forgery). If multiple identical notes appear in different places at the same time, all but one of the notes must be a forgery. All can then be treated as suspect.

Hyperlabel currency tags can be read by any Hyperlabel scanner. These scanners can be incorporated into a variety of devices to facilitate authentication and tracking, for example, automated teller machines, currency counters, and vending machines. Scanners may also be incorporated into devices such as:

-   -   Currency counters     -   Automated teller machines     -   Cash registers     -   POS checkouts     -   Mobile phone with inbuilt scanner     -   Netpage pens     -   Vending machines     -   Hyperlabel Supermarket Checkout     -   Mobile Phone with Inbuilt Scanner     -   Handheld Validity Scanner

Such scanners are multi-purpose since they can also be used to scan Hyperlabel tagged consumer goods and printed materials. A small hand-held scanner may also be used to scan and validate currency. When a scanner scans a note it notifies the currency server of the note details, the current date and time, and the scanner location (if known). Optionally, the scanner may also send the identity of the person making the cash transaction, if known. This information would be available in respect of bank transactions, currency exchanges and large cash transactions.

Currency tagging is discussed in further detail in copending patent application Ser. Nos. 11/041,651, 11/041,609, 11/041,723, 11/041,698 and 11/041,648.

Pharmaceutical Tagging

Hyperlabel tags can be printed over the entire surface of the pharmaceutical packaging, or only on a smaller area of the packaging. A Hyperlabel pharmaceutical tag contains the item's product ID and a serial number, to uniquely identify an individual item. The product ID identifies the item's National Drug Code (NDC) number. The NDC number is allocated and administered by the FDA (U.S. Food and Drug Administration) for drugs and drug-related items and identifies the product and manufacturer. Alternatively the tag may contain another product ID code, such as the European International Article Numbering (EAN) code, or EPC etc.

The pharmaceutical ID can be read by a scanner and used to look up details of the item's lot number and expiry date. Alternatively the lot number and expiry date may be contained in the pharmaceutical tag to allow off-line retrieval of this information by any scanner. The pharmaceutical ID may also be used to access details such as dosage and administration information, drug interactions, precautions, contraindications, product warnings, recall information, place of manufacture etc.

Each time a pharmaceutical item is scanned its location is recorded. This location information can be collected in a central database allowing analysis and identification of abnormal product movements and detection of counterfeit pharmaceuticals.

Suitable scanners can include:

-   -   Cash registers     -   POS checkouts     -   Mobile phone with inbuilt scanner     -   Netpage pens     -   Vending machines

Pharmaceutical tagging is discussed in further detail in copending patent applications.

Tracking

For the purpose of tracking and item validation the manufacturer, or other central authority, maintains a database which tracks the location and status of all items.

Hyperlabel scanners can be built into a variety of devices. Scanners may be fixed or mobile. A fixed scanner has a permanent, known location. A mobile scanner has no fixed location. A scanner may be on-line, i.e. have immediate access to the central database, or it may be off-line.

Scanners may be specific to a particular product application, such as a currency counter, or may be a generic Hyperlabel scanner. Hyperlabel scanners may be embedded in other multi-function devices, for example, a mobile phone or PDA.

A central database maintains up-to-date information on valid object IDs, an object ID hotlist (for all suspect object IDs), and a list of public keys corresponding to object IDs. The central server also maintains an object scanning history to track an object's movements. Each time an object is scanned, its timestamped location is recorded. If known, the details of the object owner may also be recorded. This information may be known particularly in the case of large financial transactions e.g. a large cash withdrawal from a bank. This object scanning history data can be used to detect illegal product movements, for example, the illegal import of a pharmaceutical. It can also be used to detect abnormal or suspicious product movements which may be indicative of product counterfeiting.

If an object is known to be stolen it can be immediately added to an object ID hotlist on the central server. This hotlist is automatically distributed to (or becomes accessible to) all on-line scanners, and will be downloaded to all off-line scanners on their next update. In this way the stolen status is automatically and rapidly disseminated to a huge number of outlets. Similarly, if an object is in any other way suspect it can be added to the hotlist so that its status is flagged to the person scanning the object.

An on-line scanner has instant access to the central server to allow checking of each object ID at the time of scanning. The object scanning history is also updated at the central server at the time the object is scanned.

An off-line scanner stores object status data internally to allow validation of a scanned object. The object status data includes valid ID range lists, an object ID hotlist, a public key list, and an object scanning history. Each time an object is scanned the details are recorded in the object scanning history. The object status data is downloaded from the central server, and the object scanning history is uploaded to the central server, each time the scanner connects.

A mobile scanner's location can be provided to the application by the scanner, if it is GPS-equipped. Alternatively the scanner's location can be provided by the network through which it communicates.

For example, if the hand-held scanner uses the mobile phone network, the scanner's location can be provided by the mobile phone network provider. There are a number of location technologies available. One is Assisted Global Positioning System (A-GPS). This requires a GPS-equipped handset, which receives positioning signals from GPS satellites. The phone network knows the approximate location of the handset (in this case the handset is also the scanner) from the nearest cell site. Based on this, the network tells the handset which GPS satellites to use in its position calculations. Another technology, which does not require the device to be GPS-equipped, is Uplink Time Difference of Arrival (U-TDOA). This determines the location of a wireless handset, using a form of triangulation, by comparing the time it takes a wireless handset's signal to reach several Location Measurement Units (LMUs) installed at the network's cell sites. The handset location is then calculated based on the differences in arrival times of the three (or more) signals.

Authentication

Each object ID has a signature. Limited space within the Hyperlabel tag structure makes it impractical to include a full cryptographic signature in a tag so signature fragments are distributed across multiple tags. A smaller random signature, or secret, can be included in a tag.

To avoid any vulnerability due to the limited length of the object ID, the object ID is padded, ideally with a random number. The padding is stored in an authentication database indexed by object ID. The authentication database may be managed by the manufacturer, or it may be managed by a third-party trusted authenticator.

Each Hyperlabel tag contains a signature fragment and each fragment (or a subset of fragments) can be verified, in isolation, against the object ID. The security of the signature still derives from the full length of the signature rather than from the length of the fragment, since a forger cannot predict which fragment a user will randomly choose to verify.

Fragment verification requires fragment identification. Fragments may be explicitly numbered, or may by identified by the two-dimensional coordinate of their tag, modulo the repetition of the signature across continuous tiling of tags.

Note that a trusted authenticator can always perform fragment verification, so fragment verification is always possible when on-line access to a trusted authenticator is available.

Establishing Authentication Database

Prior to allocating a new range of IDs, some setup tasks are required to establish the authentication database.

For each range of IDs a public-private signature key pair is generated and the key pair is stored in the authentication database, indexed by ID range.

For each object ID in the range the following setup is required:

-   -   generate ID padding and store in authentication database,         indexed by object ID     -   retrieve private signature key by object ID     -   generate signature by encrypting object ID and padding, using         private key     -   store signature in authentication database indexed by object ID,         and/or store the padding, since the signature can be         re-generated using the ID, padding and private key     -   encode the signature across multiple tags in repeated fashion

This data is required for the Hyperlabel tags therefore the authentication database must be established prior to, or at the time of, printing of the Hyperlabels.

Security issues are discussed in more detail above.

Off-Line Public-Key-Based Authentication

An off-line authentication device utilizes public-key signatures. The authentication device holds a number of public keys. The device may, optionally, retrieve additional public keys on demand, via a transient on-line connection when it encounters an object ID for which it has no corresponding public key signature.

For off-line authentication, the entire signature is needed. The authentication device is swiped over the Hyperlabel tagged surface and a number of tags are read. From this, the object ID is acquired, as well as a number of signature fragments and their positions. The signature is then generated from these signature fragments. The public key is looked up, from the scanning device using the object ID. The signature is then decrypted using the public key, to give an object ID and padding. If the object ID obtained from the signature matches the object ID in the Hyperlabel tag then the object is considered authentic.

The off-line authentication method can also be used on-line, with the trusted authenticator playing the role of authenticator.

On-Line Public-Key-Based Authentication

An on-line authentication device uses a trusted authenticator to verify the authenticity of an object. For on-line authentication a single tag can be all that is required to perform authentication. The authentication device scans the object and acquires one or more tags. From this, the object ID is acquired, as well as at least one signature fragment and its position. The fragment number is generated from the fragment position. The appropriate trusted authenticator is looked up by the object ID. The object ID, signature fragment, and fragment number are sent to the trusted authenticator.

The trusted authenticator receives the data and retrieves the signature from the authentication database by object ID. This signature is compared with the supplied fragment, and the authentication result is reported to the user.

On-Line Secret-Based Authentication

Alternatively or additionally, if a random signature or secret is included in each tag (or tag group), then this can be verified with reference to a copy of the secret accessible to a trusted authenticator. Database setup then includes allocating a secret for each object, and storing it in the authentication database, indexed by object ID.

The authentication device scans the object and acquires one or more tags. From this, the object ID is acquired, as well as the secret. The appropriate trusted authenticator is looked up by the object ID. The object ID and secret are sent to the trusted authenticator.

The trusted authenticator receives the data and retrieves the secret from the authentication database by object ID. This secret is compared with the supplied secret, and the authentication result is reported to the user.

Secret-based authentication can be used in conjunction with on-line fragment-based authentication is discussed in more detail above.

Product Scanning Interactions

Product Scanning at a retailer is illustrated in FIG. 44. When a store operator scans a Hyperlabel tagged product the tag data is sent to the service terminal (A). The service terminal sends the transaction data to the store server (B). The store server sends this data, along with the retailer details, to the manufacturer server (C). The Hyperlabel server knows which manufacturer server to send the message to from the object ID. On receipt of the input, the manufacturer server authenticates the object, if the manufacturer is the trusted authenticator. Alternatively the manufacturer server passes the data on to the authentication server to verify the object ID and signature (D). The authentication server sends the authentication result back to the manufacturer server (E). The manufacturer server checks the status of the object ID (against its valid ID lists and hotlist), and sends the response to the store server (F), which in turn send the result back the store service terminal (G). The store server could also communicate with the relevant authentication server directly.

The interaction detail for on-line product scanning at a retailer is shown in FIG. 45. The store operator scans the Hyperlabel tagged product. The scanner sends the scanner ID and tag data to the service terminal. The service terminal sends this data along with the terminal ID and scanner location to the store server. The store server then sends the request on to the manufacturer server, which performs authentication (either itself or via a third party authentication server) and determines the object status. The response is then sent back to the store server, and on to the operator service terminal.

The interaction detail for off-line product scanning at a retailer is shown in FIG. 46. The store operator scans the Hyperlabel tagged product. The scanner sends the scanner ID and tag data from multiple tags to the service terminal. The service terminal sends this data, along with the terminal ID and scanner location, to the store server. The store server then performs off-line authentication, as described in Section 3.4.2, and determines the object status through its cached hotlist, valid object ID lists, and public key list. The store server records the scan details in its internal object scanning history. The response is then sent back to the operator service terminal.

An alternative for off-line product scanner occurs where the scanner is a hand-held, stand-alone scanner. In this case the cached authentication data is stored within the scanner itself, and the scanner performs the validation internally. The object scanning history is also cached within the scanner. Periodically the scanner connects to the central database, uploads it's object scanning history, and downloads the latest public key list, object ID hotlist and valid ID range list. This connection may be automatic (and invisible to the user), or may be initiated by the user, for example, when the scanner is placed in a docking station/charger.

Product scanning with a netpage pen is illustrated in FIG. 47. When a user scans a Hyperlabel tagged item with their netpage pen, the input is sent to the netpage System, from the user's netpage pen, in the usual way (A). To scan a product rather than interact with it, the pen can be placed in a special mode. This is typically a one-shot mode, and can be initiated by tapping on a <scan> button printed on a netpage. Alternatively, the pen can have a user-operable button, which, when held down during a tap or swipe, tells the pen to treat the interaction as a product scan rather than a normal interaction. The tag data is transmitted from the pen to the user's netpage base station. The netpage base station may be the user's mobile phone or PDA, or it may be some other netpage device, such as a PC. The input is relayed to the Hyperlabel server (B) and then on to manufacturer server (C) in the usual way. On receipt of the input, the manufacturer server authenticates the object if the manufacturer is the trusted authenticator. Alternatively the manufacturer server passes the data on to the authentication server to verify the object ID and signature (D). The authentication server sends the authentication result back to the manufacturer server (E). The manufacturer server checks the status of the object ID (against its valid ID lists and hotlist), and sends the response to the Hyperlabel server (G). The Hyperlabel server, as part of the netpage system, can know the identity and devices of the user. The Hyperlabel server will relay the manufacturer server's response to the user's phone (G) or Web browsing device (H) as appropriate. If the user's netpage pen has LEDs then the Hyperlabel server can send a command to the user's pen to light the appropriate LED(s) (I,J).

The interaction detail for scanning with a netpage pen is shown in FIG. 48. The netpage pen clicks on the Hyperlabel tagged product. The netpage pen sends the pen id, the product's tag data and the pen's location to the Hyperlabel server. If the pen ID is not already associated with a scanner, the Hyperlabel server may create a new scanner record for the pen, or may use the pen ID as a scanner ID. The Hyperlabel server sends the scanner ID, tag data, and scanner location (if known) to the manufacturer server, which performs authentication (either itself or via a third party authentication server) and determines the object status. The response is then sent back to the Hyperlabel server, and on to the user's default Web browsing device.

Security Tagging and Tracking Object Model

The Security Tagging and Tracking object model revolves around Hyperlabel tags, object IDs, and signatures. FIG. 60 illustrates the management and organization of these objects.

As shown in FIG. 49, a Hyperlabel tag comprises a tag type, object ID, two-dimensional position and a signature fragment. The tag type indicates whether this is a tag on a common object, or whether the tag is on a special type of object such as a currency note or a pharmaceutical product. A signature fragment has an optional fragment number which identifies the fragment's place within the full signature.

As described above, a product's unique item ID may be seen as a special kind of unique object ID. The Electronic Product Code (EPC) is one emerging standard for an item ID. An item ID typically consists of a product ID and a serial number. The product ID identifies a class of product, while the serial number identifies a particular instance of that class, i.e. an individual product item. The product ID in turn typically consists of a manufacturer number and a product class number. The best-known product ID is the EAN.UCC Universal Product Code (UPC) and its variants. The Item ID class diagram is shown in FIG. 50.

Currency notes are identified by a note ID. The note ID comprises note data and a serial number. The note data identifies the type of currency, the country of issue, the note denomination, the note side (front or back) and other currency-specific information. There are two note IDs for each physical bank note—one for each side of the printed note. The Note ID class diagram is shown in FIG. 51.

Pharmaceuticals are identified by a pharmaceutical ID. Typically the pharmaceutical ID will be an EPC. A pharmaceutical ID consists of a product ID and a serial number. The product ID in turn typically consists of a manufacturer number and a product class number. The best known product ID for pharmaceutical products is the National Drug Code (NDC), allocated and administered by the US Food and Drug Administration. The Pharmaceutical ID class diagram is shown in FIG. 52.

Object Description, ownership and aggregation class diagram is shown in FIG. 53. This is described in more detail above.

The Object Scanning History class diagram is shown in FIG. 54. An object has an object scanning history, recording each time the scanner scans an object. Each object scanned event comprises the scanner ID, the date and time of the scan, and the object status at the time of the scan, and the location of the scanner at the time the object was scanned. The object status may be valid, stolen, counterfeit suspected, etc. If known, the object owner details may also be recorded.

A scanner has a unique scanner ID, a network address, owner information and a status (e.g. on-line, off-line). A scanner is either a mobile scanner, whose location may vary, or a fixed scanner, whose location is known and constant. A scanner has a current location, comprising the location details and a timestamp. A scanner may be a netpage pen, in which case it will be associated with a netpage Pen record. If a scanner in off-line, it will keep an object scanning history, and will optionally store a public key list, a valid ID range list and an object ID hotlist. The scanner class diagram is shown in FIG. 55.

The manufacturer, or other central authority, maintains a number of Object ID Hot Lists, each with a unique list ID, and the time the list was last updated. Each hot list comprises a list of suspect object IDs, comprising the object ID, date, time, status (suspected counterfeit, stolen, etc.) and other information. The Object ID Hot List class diagram is shown in FIG. 56.

The manufacturer, or other central authority, maintains a list of valid ID ranges. Each valid object ID range entry in the list comprises the start object ID and end object ID (the valid ID range) and the time the entry was updated. The Valid ID Range List class diagram is shown in FIG. 57.

The manufacturer, or other central authority, maintains a public key list. The public key list consists of a number of entries identifying the public key for a range of Object IDs. Each valid object ID range entry comprises the update time for the entry, the start object ID for the range, the end object ID for the range, and the public key applicable to each object ID in the given range. The Public Key List class diagram is shown in FIG. 58.

Object authentication may be performed by the manufacturer, or by a third-party trusted authenticator. A trusted authenticator has an authenticator ID, name and details. A trusted authenticator holds a list of public-private key pairs, each associated with one or more ID ranges. This is a list of object ID ranges (identified by the start and end ID) and the corresponding public/private signature key pair. A trusted authenticator also holds a list of secret signatures, and a list of public-key signatures. Each public-key signature identifies the actual signature and/or the padding used to generate the signature. Each secret signature and public-key signature is associated by object ID with a unique object. The Trusted Authenticator class diagram is shown in FIG. 59.

Applications

It will be appreciated that Hyperlabel tags can be used with a range of objects, including, for example, items of manufacture, pharmaceutical items, currency notes, cheques, credit or debit cards, redeemable tickets, vouchers, coupons, lottery tickets instant win tickets, or identity cards or documents, such as a driver's licenses or passports.

The identity can include at least one of an Electronic Product Code (EPC), a National Drug Code (NDC) number, a serial number of a pharmaceutical item, a currency note attribute such as a value or the like, a cheque attribute or a card attribute such as card type, issuing institution, account number, issue date, expiry date or limit.

Advantages of Hyperlabel

Unlike 2D optical barcodes that are often difficult to read due to label damage and a direct ‘line-of-sight’ requirement needed for scanning, optically readable, but invisible, infrared Hyperlabel tags, are printed all over, or on a large section of a product label. Hyperlabel tags support line-of-sight omnidirectional reading. In practice, the Hyperlabel reader is designed to scan the scanning field from at least two substantially orthogonal directions. This helps the reader to avoid occlusions which may occur if a hand is holding an item. Hyperlabel tags also incorporate Reed-Solomon error correction methods to improve reliability.

A further advantage of Hyperlabels over barcodes is that they are unobtrusive to the customer as they do not use visible label space, and tag information is not restricted to only one section of a label.

Hyperlabel tags are therefore easy to locate, easy to read, and enable accurate automatic scanning.

Hyperlabels are less promiscuous than RFID tags since they require line-of-sight for reading. This means that it will be difficult for customers to have their product scanned for information without their knowledge. Hyperlabels provide customers with the means to protect their privacy.

Hyperlabels as Interactive Web Pages

A distinctive and unique feature of Hyperlabel technology is that Hyperlabels provide the opportunity to design packaging labels as interactive ‘Web pages’—and thus make it possible for a whole new range of product-linked customer services to be introduced by the pharmaceutical industry.

When digital pen use becomes widespread, product graphics can be added to labels to indicate interactive areas and prompting customers to write or click using a Netpage pen. A digital Netpage pen can identify the x-y position on a label, and enable a link to be established between the information on the label, and a Web page on a server. The Netpage pen connects the customer to an Internet-based Hyperlabel Server through a companion device such as a mobile phone or computer.

Using a Netpage pen to interact with the label, customers can be offered additional information on drug use, risks and advice on potential interactions between drugs. It could also provide an opportunity for customers to register for participation in new drug trials, to enter promotions, to participate in Web chat sessions, or to receive ‘free’ samples. Web pages can be customized based on customer profiles, local area health data, or by using a range of product supply chain data such as geographic location.

Hyperlabels therefore make it possible for the pharmaceutical industry to extend the use of product labels and packaging to increase brand strength, and to establish closer links with customers. Thus, with Hyperlabels, the customer can become an integral part of the product supply chain, and supply chain data can be integrated with customer relationship management (CRM) or healthcare databases to improve the overall efficiency and level of service offered to customers. 

1. A method of authenticating an object, the method including steps of: receiving from a sensing device indicating data of each of a plurality of regions of a surface associated with the object, the indicating data of each region being indicative of: an identity of the object; and a signature fragment, the signature fragment being a fragment of a digital signature of at least part of the identity; determining, using the indicating data of each region, the identity, one of the signature fragments and a signature fragment identifier associated with the one signature fragment; determining a determined signature by arranging the plurality of signature fragments according to their associated signature fragment identifiers; generating, using the determined signature and a key, a generated identity; comparing the identity to the generated identity; and authenticating the object using the result of the comparison.
 2. A method according to claim 1, wherein the method includes further steps of: generating authentication data indicative of success or failure of the authentication; and transferring the authentication data to a user.
 3. A method according to claim 2, wherein the method further includes a step of transferring the authentication data to a sensing device.
 4. A method according to claim 1, wherein the digital signature is a digital signature of at least part of the identity and at least part of predetermined padding, and wherein the step of generating the generated identity includes sub-steps of: determining, using the received identity, the predetermined padding; and generating, using the predetermined padding, the key and the determined signature, the generated identity.
 5. A method according to claim 1, wherein the method includes communicating with the sensing device via at least one of: a communications network; the Internet; a mobile phone network; and, a wireless connection.
 6. A method according to claim 1, wherein the indicating data is further indicative of at least one of: a location of the respective data portion; a position of the respective data portion on the surface; a size of the data portions; a size of the signature; a size of the signature fragment; an identity of a signature fragment; units of indicated locations; redundant data; data allowing error correction; Reed-Solomon data; and, Cyclic Redundancy Check (CRC) data.
 7. A method according to claim 1, wherein the digital signature includes at least one of: a random number associated with the identity; a keyed hash of at least the identity; a keyed hash of at least the identity produced using a private key, and verifiable using a corresponding public key; cipher-text produced by encrypting at least the identity; cipher-text produced by encrypting at least the identity and a random number; and, cipher-text produced using a private key, and verifiable using a corresponding public key.
 8. A method according to claim 1, wherein the identity includes the identity of at least one of: the object; the surface; and a region of the surface.
 9. A method according to claim 1, wherein the identity includes at least one of: an Electronic Product Code (EPC); a National Drug Code (NDC) number; a serial number of a pharmaceutical item; a currency note attribute including at least one of: currency; issue country; denomination; note side; printing works; and serial number; a check attribute including at least one of: currency; issuing institution; account number; serial number; expiry date; check value; and limit; and a card attribute including at least one of: card type; issuing institution; account number; issue date; expiry date; and limit.
 10. A method according to claim 1, wherein the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout including n identical sub-layouts rotated 1/n revolutions apart about a centre of rotation, at least one sub-layout including rotation-indicating data that distinguishes that sub-layout from each other sub-layout.
 11. A method according to claim 1, wherein the coded data is arranged in accordance with at least one layout having n-fold rotational symmetry, where n is at least two, the layout encoding orientation-indicating data comprising a sequence of an integer multiple m of n symbols, where m is one or more, each encoded symbol being distributed at n locations about a centre of rotational symmetry of the layout such that decoding the symbols at each of the n orientations of the layout produces n representations of the orientation-indicating data, each representation comprising a different cyclic shift of the orientation-indicating data and being indicative of the degree of rotation of the layout. 